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For those who have indicated that drilled rotors cannot be machined, I received a message from my brother, whom is a Master Automotive Technician with over 25 years in the business. He was able to machine a set of drilled rotors without any issues. This confirms information that I had previously received from KVR Performance. The only difference when machining a drilled rotor versus a standard rotor, is to not take off as much per pass, and that's it. Otherwise, the same brake lathe was used. 
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Yes, I have had x-drilled machined before... works great!
99 T-Red SVT
***Intrax, Bilsteins, Azenis, Offroad Y, CAI, Tint, Magnaflow Exhaust, Custom Grilles, Poly Mounts, Silverstar Bulbs, 100W Ion Fogs, Focus SVT Wheels, SHO UDP, Ford Racing Wires ***
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"Absolut Rara."
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it certainly can be done, but it is much easier to screw them up.
but hey, here's an idea, don't waste your money getting them cross-drilled in the first place . . .
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CEG road warrior
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Originally posted by Rara:
it certainly can be done, but it is much easier to screw them up.
but hey, here's an idea, don't waste your money getting them cross-drilled in the first place . . .
My cross drilled rotors work tons better than the crappy stock rotors. The C/D are not warped at all. I know bigger brakes are always better but for us poor folk C/D is a good option! With all the abuse I put on my C/D...the stockers would have been garbage! 
Hector
2003 Rally Red Mitsubishi Evolution VIII
257HP/259TQ
2005 Lapis Blue Mazda 6s
RET: 00 Cabernet Red Ford Contour Zetec ATX SUPERCHARGED
160HP/141TQ
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"Absolut Rara."
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Originally posted by LoCoZ2.0:
Originally posted by Rara:
it certainly can be done, but it is much easier to screw them up.
but hey, here's an idea, don't waste your money getting them cross-drilled in the first place . . .
My cross drilled rotors work tons better than the crappy stock rotors. The C/D are not warped at all. I know bigger brakes are always better but for us poor folk C/D is a good option! With all the abuse I put on my C/D...the stockers would have been garbage!
No offense, but your statement is made out of pure ignorance; it isn't the cross-drilling that is helping you stop better or keeping your rotors from warping.
Cross drilled rotors are significantly less durable than an equivalent non-drilled rotor; they also provide a negligable change in stopping performance on a one stop scenario, and any additional cooling effect the holes may have is offset by the reduced mass of the rotor and resulting loss of heat sink mass. In other words, any benefit you have gained from them cooling off slightly quicker after you stop is offset by the fact that you need that mass in the rotor to hold the heat generated during the stop.
Cross-drilled rotors do not offer ANY appreciable performance improvement, except in very specialized cases; none of which is even remotely likely to be applicable to a street-driven contour.
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Ya, but they look beter, so they must work better. 
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"Absolut Rara."
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"Absolut Rara."
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Originally posted by Todd TCE:
Ya, but they look beter, so they must work better.
Yeah, I'm sorry, I completely neglected the "bling factor".
My bad, carry on . . . 
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Okay I guess I am stupid and have no idea what MY Contour does.  That is my opinion. I was just stating my experience. I slam on my stock rotors at higher speeds next thing you know....warped. I slam on my C/D rotors at higher speeds and nothing....they are still on my car. 
Hector
2003 Rally Red Mitsubishi Evolution VIII
257HP/259TQ
2005 Lapis Blue Mazda 6s
RET: 00 Cabernet Red Ford Contour Zetec ATX SUPERCHARGED
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That may be true, however, you do not take into account that a higher quality rotor (which is not cross-drilled) is likely to yield the same (if not better) performance and cost less.
"Cobb - It's not just for corn anymore!"
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"Absolut Rara."
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"Absolut Rara."
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Originally posted by LoCoZ2.0:
Okay I guess I am stupid and have no idea what MY Contour does. That is my opinion. I was just stating my experience. I slam on my stock rotors at higher speeds next thing you know....warped. I slam on my C/D rotors at higher speeds and nothing....they are still on my car.
are the rotors the ONLY thing you changed? Somehow I doubt it very much. Also, the basic rotor may be a different metal specification than the OEM rotor.
Try two sets of the same rotors, one set drilled and one not; use the same pads from the same production lot, same brake fluid and the same weight and weather conditions. Then test both sets back to back for stopping and fade performance. That is really the only legitimate way you could say that cross drilling was better, provided of course the test results back up your point, which they won't anyway . . .
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Function before fashion.
'96 Contour SE
"Toss the Contour into a corner, and it's as easy to catch as a softball thrown by a preschooler." -Edmunds, 1998
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Originally posted by Rara:
Originally posted by Todd TCE:
Ya, but they look beter, so they must work better.
Yeah, I'm sorry, I completely neglected the "bling factor".
My bad, carry on . . .
Ha Ha...wait, WTF?
99 Black SVT -3L Hybrid w/.5mm overbore, Spec clutch/flywheel, MSDS, BAT intake, K&N open, 17'Konig Tantrums, DMD, Opt. TB & Y, Powerslots, Bassani w/ magnaflow res.
96 SE MTX- "The War Wagon"
"I'm in love with my car..."
-Queen
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The only thing(s) I replaced were the pads and rotors. Every time I bought rotors I bought pads. Never changed or flushed the brake fluid. All it took to warp my stock rotors was to slam on the brakes at high speed (won't say what speed). I have done the same to C/D rotors (more than I can count)and nothing. Still on the car now and still not warped. I am talking out of my experience. I don't know if they work for the SVT...but they worked for my car. 
Hector
2003 Rally Red Mitsubishi Evolution VIII
257HP/259TQ
2005 Lapis Blue Mazda 6s
RET: 00 Cabernet Red Ford Contour Zetec ATX SUPERCHARGED
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"Absolut Rara."
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You can lead a horse to water . . .
You do realize that pads alone can be a dramatic difference in both feel and performance, right? Not to mention that the cast iron used for the rotors would have been of different compositions.
Repeat after me, it wasn't the cross-drilling that helped so much . . .
Its kind of like saying pickles alone make a hamburger taste so much better because you had a plain White castle burger, and then you got a burger at say, Red Robin, with pickles on it. You aren't making an valid comparison.
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Originally posted by Rara:
Its kind of like saying pickles alone make a hamburger taste so much better because you had a plain White castle burger, and then you got a burger at say, Red Robin, with pickles on it. You aren't making an valid comparison.
Mmmmmmm...burger......
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Loco,
I still don't see where you take into account the change in the base rotor itself. I bet if you had the same exact rotor, but not cross-drilled, you would see there is little difference between the two. If anything, I bet performance would be slightly better in the non cross-drilled if put to rigorous scientific tests.
"Cobb - It's not just for corn anymore!"
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The only value added aspect of the drilling that could contribute to the overall stopping of the brakes is the 'self cleaning' aspect of the holes to the pad surface. Same as adding the slots to rotors. This helps vent the boundary layer built up between the pad and rotor as well as contributing slightly to wiping the pad clean as it goes 'round.
Still, any gains in brake torque are far more likely due to pad Cf than any holes or slots.
Did I mention they look cool?
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Originally posted by Rara:
You can lead a horse to water . . .
Maddening, ain't it? Let's talk about...strut tower braces!
Pacific Green '96 Contour LX V6
â??98 GTP, light mods, 14.66/94
Calypso Green '92 Mustang LX coupe, 13.56/101
Crown Autocross Club 1999 Street Tire Champion, 2000/2001/2002 Street Modified Champion
KCR SCCA 2002 Solo II Street Modified Champion
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"Absolut Rara."
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Originally posted by MFE:
Originally posted by Rara:
You can lead a horse to water . . .
Maddening, ain't it? Let's talk about...strut tower braces!
lmao, "but, I can FEEL it making it andle better . . ."
back to the rotors, at least our resident brake vendor only touts the one true benefit of cross drilled rotors, unlike vendors at other sites . . .
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Originally posted by Rara:
Originally posted by MFE:
Originally posted by Rara:
You can lead a horse to water . . .
Maddening, ain't it? Let's talk about...strut tower braces!
lmao, "but, I can FEEL it making it andle better . . ."
back to the rotors, at least our resident brake vendor only touts the one true benefit of cross drilled rotors, unlike vendors at other sites . . .
Baer and Stoptech are two other companies I know of who are glad to 1) give you the real info, and 2) sell you cross-drilled stuff anyway (because it looks cool...).
Function before fashion.
'96 Contour SE
"Toss the Contour into a corner, and it's as easy to catch as a softball thrown by a preschooler." -Edmunds, 1998
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Oh well.
Hector
2003 Rally Red Mitsubishi Evolution VIII
257HP/259TQ
2005 Lapis Blue Mazda 6s
RET: 00 Cabernet Red Ford Contour Zetec ATX SUPERCHARGED
160HP/141TQ
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LoCo, we're on to you. At least I am. I've seen the pattern. You'd rather keep arguing than admit you were wrong. Which you are.
Pacific Green '96 Contour LX V6
â??98 GTP, light mods, 14.66/94
Calypso Green '92 Mustang LX coupe, 13.56/101
Crown Autocross Club 1999 Street Tire Champion, 2000/2001/2002 Street Modified Champion
KCR SCCA 2002 Solo II Street Modified Champion
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cross drilled and/or slotted rotors do look really sweet behind a set of big wheels though. thats fo sho! 
thanks to cawong for use of the pic.
Oo (xxx)oO
o xxxxxxxx o
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"Absolut Rara."
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RogerB, I was actually referring to a guy on an Altima board, there was a rather long thread there that was linked to another board that both MFE and I are regulars on.
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Originally posted by Rara:
RogerB, I was actually referring to a guy on an Altima board, there was a rather long thread there that was linked to another board that both MFE and I are regulars on.
Oh, no argument, here. There are good vendors and snake-oil salesmen. Just wanted to mention two other good, honest companies.
Function before fashion.
'96 Contour SE
"Toss the Contour into a corner, and it's as easy to catch as a softball thrown by a preschooler." -Edmunds, 1998
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Originally posted by Rara:
any additional cooling effect the holes may have is offset by the reduced mass of the rotor and resulting loss of heat sink mass. In other words, any benefit you have gained from them cooling off slightly quicker after you stop is offset by the fact that you need that mass in the rotor to hold the heat generated during the stop.
I wish someone had told me this before I bought them, when I was asking this exact question about whether they would dissipate heat better.
Maybe in prolonged moderate braking, the holes do a little good... not enough that I've ever noticed it helping, of course.
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Originally posted by mikey boy:
cross drilled and/or slotted rotors do look really sweet behind a set of big wheels though. thats fo sho!
Yeah, until you put big wheels on cross-drilled rotors that are still the stock size, as on mine... then the first thing anyone thinks when they see your cool perforated rotors is "god those rotors look tiny, don't they?"
I really want rotors about 2" bigger. But I have a choice between rotors less than 1" bigger (CSVT) and rotors probably too big for my E0 rims (FSVT).
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yeah paul you have to get the big ones for that "bling" factor. 13" cross drilled rotors would look nice.
Oo (xxx)oO
o xxxxxxxx o
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A bit of history.... All of this makes fun reading keep in mind.
About ten years ago now I first started producing the SHO kits after I left Bondurant. Took them to the conventions and such to pedal them. Others there were selling the 'soon to be the norm' drilled rotors in stock size. (this was when companies like ****** were tiny and finding the nitch in drilling Chinese rotors, plating them and selling them to kids!) So, when I was asked why I did not offer them drilled on the SHO kits I replied that they were too risky and short lived that I'd prefer not to. In fact for many years I REFUSED to. Well....what do I know? That big shop in *** offers them and they know the SHO (just ask em) and THEY sell them so I must be high!
As time went by (years that is) I caved in and did a few. And I also heard the horror stories of all those ones sold by **** and ***** that cracked or nearly exploded! I also found that new kits like the Eclipse and Impala were also asking for it. Others such as ****** and ****** were selling them! Well, common sense and a mortgage over ruled my better judgement and I now offer them. Do I push them? Nope. Do I run them? Yup. On a 1500lb race car. And for weight reduction only.
Do you need them. Nope. But hey, there's always Turbo Grooves and Heat Slots (wtf is that??) not to mention other buzz words. Let's face it, if one of us doesn't offer it the other will and it's still a business.
BTW, did I mention they look cool?
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Originally posted by Todd TCE:
A bit of history.... All of this makes fun reading keep in mind.
About ten years ago now I first started producing the SHO kits after I left Bondurant. Took them to the conventions and such to pedal them. Others there were selling the 'soon to be the norm' drilled rotors in stock size. (this was when companies like ****** were tiny and finding the nitch in drilling Chinese rotors, plating them and selling them to kids!) So, when I was asked why I did not offer them drilled on the SHO kits I replied that they were too risky and short lived that I'd prefer not to. In fact for many years I REFUSED to. Well....what do I know? That big shop in *** offers them and they know the SHO (just ask em) and THEY sell them so I must be high!
As time went by (years that is) I caved in and did a few. And I also heard the horror stories of all those ones sold by **** and ***** that cracked or nearly exploded! I also found that new kits like the Eclipse and Impala were also asking for it. Others such as ****** and ****** were selling them! Well, common sense and a mortgage over ruled my better judgement and I now offer them. Do I push them? Nope. Do I run them? Yup. On a 1500lb race car. And for weight reduction only.
Do you need them. Nope. But hey, there's always Turbo Grooves and Heat Slots (wtf is that??) not to mention other buzz words. Let's face it, if one of us doesn't offer it the other will and it's still a business.
BTW, did I mention they look cool?
Pay attention to the man. He knows his ****.
Sorry about that, I couldn't help myself. But all kidding aside, he knows what most in the business already know, that drilled rotors are really more for looks than anything else. I don't want them on my car, even for looks. Brakes are just too much of a safety issue.
Jim Johnson
98 SVT
03 Escape Limited
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Originally posted by MFE:
LoCo, we're on to you. At least I am. I've seen the pattern. You'd rather keep arguing than admit you were wrong. Which you are.
Keep your comments to yourself.
Hector
2003 Rally Red Mitsubishi Evolution VIII
257HP/259TQ
2005 Lapis Blue Mazda 6s
RET: 00 Cabernet Red Ford Contour Zetec ATX SUPERCHARGED
160HP/141TQ
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I have no life
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so if drilled rotors are bad? how about just slotted, dem any good? and how much does a full FSVT brake conversion cost (i also have to change drums to discs in rear)? thankz.
98.5 SVT
91 Escort GT (almost sold)
96 ATX Zetec (i brake to watch you swerve)
FS: SVT rear sway bar
WTB: Very cheap beater
CEG Dragon Run - October 13-15
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Originally posted by Todd TCE:
A bit of history.... All of this makes fun reading keep in mind.
About ten years ago now I first started producing the SHO kits after I left Bondurant. Took them to the conventions and such to pedal them. Others there were selling the 'soon to be the norm' drilled rotors in stock size. (this was when companies like ****** were tiny and finding the nitch in drilling Chinese rotors, plating them and selling them to kids!) So, when I was asked why I did not offer them drilled on the SHO kits I replied that they were too risky and short lived that I'd prefer not to. In fact for many years I REFUSED to. Well....what do I know? That big shop in *** offers them and they know the SHO (just ask em) and THEY sell them so I must be high!
As time went by (years that is) I caved in and did a few. And I also heard the horror stories of all those ones sold by **** and ***** that cracked or nearly exploded! I also found that new kits like the Eclipse and Impala were also asking for it. Others such as ****** and ****** were selling them! Well, common sense and a mortgage over ruled my better judgement and I now offer them. Do I push them? Nope. Do I run them? Yup. On a 1500lb race car. And for weight reduction only.
Do you need them. Nope. But hey, there's always Turbo Grooves and Heat Slots (wtf is that??) not to mention other buzz words. Let's face it, if one of us doesn't offer it the other will and it's still a business.
BTW, did I mention they look cool?
This is a good example of human nature. Everywhere in life this situation will present itself over and over again in different forms (philosophically speaking  ). Cynical though it may seem, you can show a man all the evidence in the world and it makes no sense until it happens to him. The way I see it, expect the worst from people until you learn otherwise...then you'll never be blind-sided with surprises unless they're good ones.
Todd, you have been very honest on this board and that is something I am very happy about. I read and learn and I am thankful for it.
BTW, cross-drilled rotors? Not me. Not that they don't look cool, I'm just too cheap to spend money if it doesn't it doesn't change my performance numbers. That's not to say I don't spend money, just I want to have some effect for it other than BlingBling.
Tom
Former owner of '99 CSVT - Silver #222/2760
356/334 wHP/TQ at 10psi on pump gas!
See My Mods
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Cross-drilled rotors sure am good mm-hmmm:    These are rotors on a Maxima that are nearly two inches bigger than stock so technically they should be better at handling thermal energy despite the holes, and guess what, they cracked anyway. The lessons here are 1) Cross-drilling REDUCES THE THERMAL CAPACITY of the rotor due to decreased mass, therefore overall braking capacity is REDUCED compared to same-size, same-composition rotors that are not drilled. 2) Cross drilling compromises the integrity and therefore the safety of the rotors even if they are big enough to accomodate the heat 3) Stay away from cross-drilled rotors. unless you live in LoCoLand where earthly physics don't apply...
Pacific Green '96 Contour LX V6
â??98 GTP, light mods, 14.66/94
Calypso Green '92 Mustang LX coupe, 13.56/101
Crown Autocross Club 1999 Street Tire Champion, 2000/2001/2002 Street Modified Champion
KCR SCCA 2002 Solo II Street Modified Champion
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It's not really the thermal mass of the rotor that causes the cracks, it's the difference in temps of the iron around the holes and their changes in expansion/contraction. You have a 750 degree rotor and 75 degree air blasting through it. They don't like that kind of stuff.
For street looks and use they are fine. For extended track use they should be avoided.
If you want to take it to the next level, the rotors shouldn't be bolted to the hats either. Floating rotors are the ultimate answer. And price.
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I know it's not the thermal mass that causes the cracks, it's the stress risers caused by drilling them and the uneven cooling that results from the holes being there. Just another reason not to do it.
Pacific Green '96 Contour LX V6
â??98 GTP, light mods, 14.66/94
Calypso Green '92 Mustang LX coupe, 13.56/101
Crown Autocross Club 1999 Street Tire Champion, 2000/2001/2002 Street Modified Champion
KCR SCCA 2002 Solo II Street Modified Champion
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"Absolut Rara."
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Yeah, when you've upsized the rotor, the loss of thermal mass rarely becomes an issue; that really only comes into play when you cross-drill a stock size rotor that is borderline for thermal capacity.
And yeah, the cracks are due to a combination of uneven cooling and the additional stress concentration right at the points where the cooling differential is the worst.
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Originally posted by MFE:
Whaddya gonna do, CRY? Why don't YOU keep YOUR crackhead comments to YOURself? You're talking out your ass on this one and anyone who follows your advice does so at their peril, but the uninitiated might not know that if it weren't pointed out
Fer chrissake, all he said was his EXPERIENCE, that the plain rotors he used warped, and the particular drilled rotors he used did not. Why not take that as a point of real-world data, instead of throwing a tantrum? You can argue about theories and generalities all day, but you can't argue with what has actually happened. That's like trying to prove that the Raiders had to have won the super bowl, after it's been played.
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I think he was referring to the fact that Loco told MFE to keep his comments to himself.
Sometimes this place has more drama then the finales of American Idol and The Bachelor combined. 
"Cobb - It's not just for corn anymore!"
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"Absolut Rara."
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Originally posted by Paul Kienitz:
That's like trying to prove that the Raiders had to have won the super bowl, after it's been played.
No, that's like trying to prove the Raiders won the World Series after its been played. The two aren't comparable.
Loco made a comparison after changing many, many factors involved, and then attributed ALL of the changes to a SINGLE factor; a factor which has been proven to be ineffective at improving performance and potentially dangerous by many experts in the brake industry, both OEM and aftermarket. I think it is an excessively flawed comparison. No one doubts Loco's experience, only his interpretation of it.
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I have no life
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Originally posted by Kremithefrog:
so if drilled rotors are bad? how about just slotted, dem any good? and how much does a full FSVT brake conversion cost (i also have to change drums to discs in rear)? thankz.
^^^^^^^^^^
98.5 SVT
91 Escort GT (almost sold)
96 ATX Zetec (i brake to watch you swerve)
FS: SVT rear sway bar
WTB: Very cheap beater
CEG Dragon Run - October 13-15
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"Absolut Rara."
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"Absolut Rara."
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Originally posted by Kremithefrog:
Originally posted by Kremithefrog:
so if drilled rotors are bad? how about just slotted, dem any good? and how much does a full FSVT brake conversion cost (i also have to change drums to discs in rear)? thankz.
^^^^^^^^^^
Slotted is not nearly as bad, though it does still introduce some stress concentration locations. Performance gains are still minimal, except in special circumstances.
On the FSVT stuff, and drums to discs, try searching, both questions have been answered numerous times in the recent past.
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but i'm lazy, and i thought most people going to FSVT brakes already had discs in rear, so I figured it may cost me a bit more..... Time for more fsvts to be made and start showing up in junkyards. 
98.5 SVT
91 Escort GT (almost sold)
96 ATX Zetec (i brake to watch you swerve)
FS: SVT rear sway bar
WTB: Very cheap beater
CEG Dragon Run - October 13-15
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Originally posted by Rara:
Loco made a comparison after changing many, many factors involved, and then attributed ALL of the changes to a SINGLE factor;
Where did he do that? I don't remember him doing anything of the kind.
I guess "many, many" is your way of saying "two".
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Originally posted by Paul Kienitz:
Originally posted by Rara:
Loco made a comparison after changing many, many factors involved, and then attributed ALL of the changes to a SINGLE factor;
Where did he do that? I don't remember him doing anything of the kind.
I guess "many, many" is your way of saying "two".
Solid, OEM? rotors and stock pads to aftermarket pads, rotors, (with holes). That's at least 3 factors that we know of.
Function before fashion.
'96 Contour SE
"Toss the Contour into a corner, and it's as easy to catch as a softball thrown by a preschooler." -Edmunds, 1998
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"Absolut Rara."
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"Absolut Rara."
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Originally posted by Paul Kienitz:
Originally posted by Rara:
Loco made a comparison after changing many, many factors involved, and then attributed ALL of the changes to a SINGLE factor;
Where did he do that? I don't remember him doing anything of the kind.
I guess "many, many" is your way of saying "two".
Well, lets see what factors were changed.
1. Rotor design
2. Rotor material
3. Rotor manufacturing Process
4. Cross-drilling
5. friction material composition
6. friction coefficient
7. friction material metal content
8. Pad thickness
9. friction material compressibility
10. Pad design (ie slots, grooves, chamfers etc. on the friction material)
11. Pad bonding layer composition
12. Age of compenents being compared (ie old OEM vs. new aftermarket)
13. Usage conditions
14. Pad/rotor burnish procedure/condition
I dunno man, that's 14 off the top of my head. All of which can significntly affect the situation, yet loco attributed ALL of the difference to the cross-drilling. Hardly a valid comparison.
btw, I would think that 14 would qualify as "many, many", but if that's not enough for you I'm sure I could spend a bit more than 30 seconds thinking about them and come up with a few more. I mean, it's not like I do this stuff for a living.
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Originally posted by Rara:
Well, lets see what factors were changed.
...
I dunno man, that's 14 off the top of my head. All of which can significntly affect the situation, yet loco attributed ALL of the difference to the cross-drilling. Hardly a valid comparison.
Your list of 14 is very padded, since most of them add up to either "different rotor blank" or "different pad"... but that's not what I'm objecting to. First of all, you are assuming that the x-drilled rotors must have been used with different kinds of pads than the solid rotors were. But Hector said he changed the rotors and pads multiple times before trying a cross-drilled rotor; it seems likely to me that he would have settled on a preferred pad a couple of changes earlier. Now you could have asked if he used the same pad brand, but nooooooo.
Second, and more important, you are once again repeathing the charge that "loco attributed ALL of the difference to the cross-drilling". Now this time, how about you answer the question you ignored last time: WHERE did he do that? I see no such claim in anything he wrote!
Originally posted by Rara:
btw, I would think that 14 would qualify as "many, many", but if that's not enough for you I'm sure I could spend a bit more than 30 seconds thinking about them and come up with a few more. I mean, it's not like I do this stuff for a living.
Knock yourself out, the list still adds up to two factors in practice, or three if you assume the pads must be different. You can't after all, order a rotor with specs like "I'd like it just the same as an OEM rotor, only 1 mm thicker and with a different burnishing procedure." Since these factors are not separable at the parts store, separating them out to inflate your list is just dorky.
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You're missing the point at hand by a country mile, in your effort to emulate Mighty Mouse and save the day. Let me summarize:
Rara: "Cross drilled rotors are no good"
Loco: "My crossdrilled rotors are way better than stock ones"
Rara: "Cross drilled rotors are no good, and here's the solid facts about why (for the thousandth time and you know it)
Loco: Then I must be dumb [ding!] because my stock rotors warped, and my cross drilled ones haven't [so there!]
Rara: "There are a lot of other factors involved; the cross drilling did not make for the improvement, and here's why (for the thousand-and-first time)
Loco: [grasping feverishly at straws in a failed attempt to win this argument in the face of hard facts from brake engineers themselves, one of them active in this thread] The only thing I changed was the rotors and they're better and they haven't warpd" [DOUBLE so there!!]
Now...here's the pattern in full peacock display. Loco is wrong, but he will not admit it. Physics are different where he lives.
Several more citations and examples are given, by brake engineers and mere mortals with a grasp of how things work, which show this display to be the mockery that it is, but he ignores it because He Can't Bear to Lose. Must...hang...on....to tenuous...position...
Loco: "Oh well" [la la la la la I can't hear you la la la la]
And then you come along to save the day, taking this EXPERIENCE (smelling very cooked up in an effort to win an argument) over "theories and generalities" LOL...you really appeared smarter than that at first. So in the immortal words of Loco..."oh well".
Read the links that people have taken the time to post for your benefit and see if they sound like "generalities and theories".
Failing that...wanna buy a strut tower brace? Your car will corner flatter! Ask Loco
In all fairness to Loco, I may have confused him with someone else when I made the comment about the pattern. Truth be told, I probably confused him with any number of people here who exhibit that pattern. It's not hard to spot, but it's hard to keep everyone straight.
Pacific Green '96 Contour LX V6
â??98 GTP, light mods, 14.66/94
Calypso Green '92 Mustang LX coupe, 13.56/101
Crown Autocross Club 1999 Street Tire Champion, 2000/2001/2002 Street Modified Champion
KCR SCCA 2002 Solo II Street Modified Champion
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"Absolut Rara."
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Thanks MFE, lol, excellent summary, except you missed Paul . . . Paul, Ok, if you wish, I will address your points. Originally posted by Paul Kienitz:
Your list of 14 is very padded, since most of them add up to either "different rotor blank" or "different pad"...
Maybe, but each different rotor and each different pad make up a completely different arrangement of those items, and any single one can have a significant effect on brake performance, pad life, and rotor life. This is why they were all listed, the fact that a particular pad you buy off the shelf has a pre-determined organization of those items makes little difference.
Originally posted by Paul Kienitz:
First of all, you are assuming that the x-drilled rotors must have been used with different kinds of pads than the solid rotors were. But Hector said he changed the rotors and pads multiple times before trying a cross-drilled rotor; it seems likely to me that he would have settled on a preferred pad a couple of changes earlier. Now you could have asked if he used the same pad brand, but nooooooo.
You are correct here, in that I did make an assumption; but I certainly don't believe it unfounded. Loco has recently mentioned his cross-drilled rotors and how great he thinks they are numerous times, and virtualy every single time, he has referred to them along with his "new" Autospecialty heavy duty pads. An assumption was made, but hardly a leap at all.
Originally posted by Paul Kienitz:
Second, and more important, you are once again repeathing the charge that "loco attributed ALL of the difference to the cross-drilling". Now this time, how about you answer the question you ignored last time: WHERE did he do that? I see no such claim in anything he wrote!
Hmm, have we been reading the same thread? Maybe I need to recap.
Originally posted by LoCoZ2.0:
My cross drilled rotors work tons better than the crappy stock rotors. The C/D are not warped at all.
Originally posted by LoCoZ2.0:
. . .but for us poor folk C/D is a good option! With all the abuse I put on my C/D...the stockers would have been garbage!
Originally posted by LoCoZ2.0:
I slam on my stock rotors at higher speeds next thing you know....warped. I slam on my C/D rotors at higher speeds and nothing....they are still on my car.
Originally posted by LoCoZ2.0:
All it took to warp my stock rotors was to slam on the brakes at high speed . . . I have done the same to C/D rotors (more than I can count)and nothing.
And From another thread:
Originally posted by LoCoZ2.0:
Originally posted by DemonSVT:
You are much better off with a quality full face rotor.
Slotted and expecially drilled rotors are just for looks!
You would think so but NO! I have had my Powerstop C/D rotors on for about a year and high speed braking is greatly improved and NO WARPING. Not even much fade on Gingerman!
And Another thread here:
Originally posted by LoCoZ2.0:
HELL NO! I know this first hand. I have had 2 sets of stock replacements and BOTH warped due to normal street driving. I put a set of crossdrilled and no warping in street driving, road racing, or drag racing.
I think that is more than plenty to show the LoCo is attributing his "fantastic" brakes to the cross-drilling on the rotors. Or at least that is what he is telling the rest of the world . . .
Originally posted by Paul Kienitz:
Knock yourself out, the list still adds up to two factors in practice, or three if you assume the pads must be different.
No, it still adds up to 14 in practice, just because you don't deal with them seperately doesn't mean they aren't seperate things.
Originally posted by Paul Kienitz:
You can't after all, order a rotor with specs like "I'd like it just the same as an OEM rotor, only 1 mm thicker and with a different burnishing procedure." Since these factors are not separable at the parts store, separating them out to inflate your list is just dorky.
Actually, you can to some degree (well except for the burnishing part, because that isn't done until you put the rotors and pads on the car). Though they come in predetermined combinations, kind of like option packages when you order a car. Just because you order the "Power Package" as one item, doesn't mean that power windows and power door locks are two different things. And trust me, if I wanted to sound "dorky by inflating my list" I could increase the one item "friction material composition" to about a hundred seperate items, and I know less about friction material than I do the rest of the brake system . . . Btw, I think I know who took the red pill . . . or at least two of them anyway.
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"Absolut Rara."
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You know, after re-perusing this thread, I swear I've had this "discussion before, but on a different car part . . . a mass air sensor maybe?
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CEG road warrior
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Originally posted by Rara:
Thanks MFE, lol, excellent summary, except you missed Paul . . .
Paul,
Ok, if you wish, I will address your points.
Originally posted by Paul Kienitz:
Your list of 14 is very padded, since most of them add up to either "different rotor blank" or "different pad"...
Maybe, but each different rotor and each different pad make up a completely different arrangement of those items, and any single one can have a significant effect on brake performance, pad life, and rotor life. This is why they were all listed, the fact that a particular pad you buy off the shelf has a pre-determined organization of those items makes little difference.
Originally posted by Paul Kienitz:
First of all, you are assuming that the x-drilled rotors must have been used with different kinds of pads than the solid rotors were. But Hector said he changed the rotors and pads multiple times before trying a cross-drilled rotor; it seems likely to me that he would have settled on a preferred pad a couple of changes earlier. Now you could have asked if he used the same pad brand, but nooooooo.
You are correct here, in that I did make an assumption; but I certainly don't believe it unfounded. Loco has recently mentioned his cross-drilled rotors and how great he thinks they are numerous times, and virtualy every single time, he has referred to them along with his "new" Autospecialty heavy duty pads. An assumption was made, but hardly a leap at all.
Originally posted by Paul Kienitz:
Second, and more important, you are once again repeathing the charge that "loco attributed ALL of the difference to the cross-drilling". Now this time, how about you answer the question you ignored last time: WHERE did he do that? I see no such claim in anything he wrote!
Hmm, have we been reading the same thread? Maybe I need to recap.
Originally posted by LoCoZ2.0:
My cross drilled rotors work tons better than the crappy stock rotors. The C/D are not warped at all.
Originally posted by LoCoZ2.0:
. . .but for us poor folk C/D is a good option! With all the abuse I put on my C/D...the stockers would have been garbage!
Originally posted by LoCoZ2.0:
I slam on my stock rotors at higher speeds next thing you know....warped. I slam on my C/D rotors at higher speeds and nothing....they are still on my car.
Originally posted by LoCoZ2.0:
All it took to warp my stock rotors was to slam on the brakes at high speed . . . I have done the same to C/D rotors (more than I can count)and nothing.
And From another thread:
Originally posted by LoCoZ2.0:
Originally posted by DemonSVT:
You are much better off with a quality full face rotor.
Slotted and expecially drilled rotors are just for looks!
You would think so but NO! I have had my Powerstop C/D rotors on for about a year and high speed braking is greatly improved and NO WARPING. Not even much fade on Gingerman!
And Another thread here:
Originally posted by LoCoZ2.0:
HELL NO! I know this first hand. I have had 2 sets of stock replacements and BOTH warped due to normal street driving. I put a set of crossdrilled and no warping in street driving, road racing, or drag racing.
I think that is more than plenty to show the LoCo is attributing his "fantastic" brakes to the cross-drilling on the rotors. Or at least that is what he is telling the rest of the world . . .
Originally posted by Paul Kienitz:
Knock yourself out, the list still adds up to two factors in practice, or three if you assume the pads must be different.
No, it still adds up to 14 in practice, just because you don't deal with them seperately doesn't mean they aren't seperate things.
Originally posted by Paul Kienitz:
You can't after all, order a rotor with specs like "I'd like it just the same as an OEM rotor, only 1 mm thicker and with a different burnishing procedure." Since these factors are not separable at the parts store, separating them out to inflate your list is just dorky.
Actually, you can to some degree (well except for the burnishing part, because that isn't done until you put the rotors and pads on the car). Though they come in predetermined combinations, kind of like option packages when you order a car. Just because you order the "Power Package" as one item, doesn't mean that power windows and power door locks are two different things. And trust me, if I wanted to sound "dorky by inflating my list" I could increase the one item "friction material composition" to about a hundred seperate items, and I know less about friction material than I do the rest of the brake system . . . Btw, I think I know who took the red pill . . . or at least two of them anyway.
I guess I can't have an opinion. I had tried different stock replacement for pads and rotors and ALWAYS the same thing-warping. I got the cross drilled rotors and heavy duty pads and no warping. I never said it wasn't because of the pad material OR rotor material...I just stated that I had a great experience with them (never pointing out one factor...because it is a combination of ALL factors). As you can see I never said that JUST BECAUSE they were cross drilled they were better than non C/D....everyone just assumed that and you know where that gets you.
Hector
2003 Rally Red Mitsubishi Evolution VIII
257HP/259TQ
2005 Lapis Blue Mazda 6s
RET: 00 Cabernet Red Ford Contour Zetec ATX SUPERCHARGED
160HP/141TQ
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Technically speaking,
With the right alloy compound,
C/D rotors would be beneficial.
The right alloy would need a high thermal capacity,
low external thermal conducivity, high internal thermal conductivity, and really high thermal expansion.
Just a thought.
Frank McCoy aka Mod-deth aka Mid Life Crisis aka SVT Doood aka mcgainer is a SCAM ARTIST
Pre98 Zetec - Some Mods
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"Absolut Rara."
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Originally posted by SleeperZ:
and really high thermal expansion.
Nope, that alone would make the cracking problem worse.
And Loco, I think I demonstrated very clearly, with your own words that you attributed your improvements to the cross drilling, or at least publicly portrayed it that way.
And while you are certainly welcome to your opinion, it does not mean your opinion is right or is even technically feasible, and I think that I, and others, have proven that clearly enough.
Except in very special circumstances, such as a motorcycle, or a race car with extremely large rotors, and cast in holes rather than drilled, cross-drilling your rotors provides little or no benefit to performance at best, makes the rotor significantly more prone to cracking, and if unchecked catastrophic failure, with the only potential benefit being appearance.
But, of course, since you state it is your "opinion" it makes it ok to spread BS, because, as your opinion, it is completely impossible to be wrong. Hmm, maybe my opinion should be that if you smear cream cheese all over the hood of your car, it will create a low pressure effect in front of the car that will pull it along at high speed, drastically improving top speed and fuel mileage. That's my opinion, so I need no technical feasibility to back it, its just true.
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Originally posted by Rara:
Originally posted by SleeperZ:
and really high thermal expansion.
Nope, that alone would make the cracking problem worse.
And Loco, I think I demonstrated very clearly, with your own words that you attributed your improvements to the cross drilling, or at least publicly portrayed it that way.
And while you are certainly welcome to your opinion, it does not mean your opinion is right or is even technically feasible, and I think that I, and others, have proven that clearly enough.
Except in very special circumstances, such as a motorcycle, or a race car with extremely large rotors, and cast in holes rather than drilled, cross-drilling your rotors provides little or no benefit to performance at best, makes the rotor significantly more prone to cracking, and if unchecked catastrophic failure, with the only potential benefit being appearance.
But, of course, since you state it is your "opinion" it makes it ok to spread BS, because, as your opinion, it is completely impossible to be wrong. Hmm, maybe my opinion should be that if you smear cream cheese all over the hood of your car, it will create a low pressure effect in front of the car that will pull it along at high speed, drastically improving top speed and fuel mileage. That's my opinion, so I need no technical feasibility to back it, its just true.
Ok Rara  , I can't stay out of this argument any longer. You are completely wrong.  It's not cream cheese. Geez. It's butter. And if you want to get technical about it a better butter option would be synthetic butter, margarine. 
-- 1999 SVT #220 --
In retrospect, it was all downhill from here. RIP, CEG.
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Originally posted by LoCoZ2.0:
I guess I can't have an opinion. I had tried different stock replacement for pads and rotors and ALWAYS the same thing-warping. I got the cross drilled rotors and heavy duty pads and no warping. I never said it wasn't because of the pad material OR rotor material...I just stated that I had a great experience with them (never pointing out one factor...because it is a combination of ALL factors). As you can see I never said that JUST BECAUSE they were cross drilled they were better than non C/D....everyone just assumed that and you know where that gets you.
1) Learn critical thinking.
2) Learn about the scientific method.
From all appearances, it certainly seems that you are attributing the results to the holes. If you weren't then you would say something like, "My stock replacements warped, but my KVR's didn't." Instead, you stress over and over how they are crossdrilled. Language is a funny thing.
Of course you are entitled to your opinion, but it's a free country, and people are entitled to argue with you. If their "opinion" is backed up by hundreds of years of accumulated knowledge, engineering, racing experience, and sound scientific testing, and yours is not, you will probably lose the argument.
Of course, you could always appeal to Congress. They eat junk science for lunch every day.
Function before fashion.
'96 Contour SE
"Toss the Contour into a corner, and it's as easy to catch as a softball thrown by a preschooler." -Edmunds, 1998
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"Absolut Rara."
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Originally posted by bigMoneyRacing:
Ok Rara , I can't stay out of this argument any longer. You are completely wrong. It's not cream cheese. Geez. It's butter. And if you want to get technical about it a better butter option would be synthetic butter, margarine.
You are correct, the butter, and further synthetic butter, will reduce the drag coefficient more than the cream cheese, and give even better fuel mileage, but the more rough texture of the cream cheese breaks up the boundary layer of the airflow, creating more negative pressure than the butter(s) and therefore an even higher top end speed.
So, both work well, it just depends on what you are after
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"Absolut Rara."
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Originally posted by LoCoZ2.0:
I guess I can't have an opinion. I had tried different stock replacement for pads and rotors and ALWAYS the same thing-warping. I got the cross drilled rotors and heavy duty pads and no warping. I never said it wasn't because of the pad material OR rotor material...I just stated that I had a great experience with them (never pointing out one factor...because it is a combination of ALL factors). As you can see I never said that JUST BECAUSE they were cross drilled they were better than non C/D....everyone just assumed that and you know where that gets you.
Ok, one more thing on this one. How do you know they were warping? And were not experiencing excessive DTV (disc thickness variation)? I doubt very very much you would even have a clue as to the difference, or that they are caused by very different things.
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Originally posted by Rara:
Originally posted by SleeperZ:
and really high thermal expansion.
Nope, that alone would make the cracking problem worse.
I think not.
One should fully understand thermodynamics before teaching it.
With the proper alloy, a C/D rotor WITH high thermal expansion (and with the other properties I described above as well as a few I didn't describe) would expand into the holes, not outward.
This would only be possible with an alloy that would transfer heat into inner layers of the rotor, where a heat sink is mounted between the 2 sides of the rotor.
(To better understand the statement above; Think of a brake rotor as a stack of 3 pancakes, the top pancake transfers heat to the middle pancake, which inturn transfers heat to the bottom pancake. Finally the bottom pancake transfer heat to the plate. And the plate disipates the heat.)
Frank McCoy aka Mod-deth aka Mid Life Crisis aka SVT Doood aka mcgainer is a SCAM ARTIST
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Originally posted by SleeperZ:
Originally posted by Rara:
Originally posted by SleeperZ:
and really high thermal expansion.
Nope, that alone would make the cracking problem worse.
I think not.
One should fully understand thermodynamics before teaching it.
With the proper alloy, a C/D rotor WITH high thermal expansion (and with the other properties I described above as well as a few I didn't describe) would expand into the holes, not outward.
This would only be possible with an alloy that would transfer heat into inner layers of the rotor, where a heat sink is mounted between the 2 sides of the rotor.
(To better understand the statement above; Think of a brake rotor as a stack of 3 pancakes, the top pancake transfers heat to the middle pancake, which inturn transfers heat to the bottom pancake. Finally the bottom pancake transfer heat to the plate. And the plate disipates the heat.)
Sounds cool. Can you make 'em without the holes? I'll take four.
Function before fashion.
'96 Contour SE
"Toss the Contour into a corner, and it's as easy to catch as a softball thrown by a preschooler." -Edmunds, 1998
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So your telling Rara how brakes work? 
I think he pretty much has that figured out by now.
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SleeperZ, you're only addressing (weakly) the issue of cracking. You are conveniently ignoring the primary issue at hand, for what must now be the thousand-and-third time: Brakes work by converting kinetic energy to heat energy through the use of friction.
The more heat energy the rotors can accept, the more braking power you have.
Cross-drilling reduces mass more than they add cooling capacity thanks to the holes.
Reduced mass means reduced heat sink.
Reduced heat sink means the rotors can't accept as much heat energy. Therefore reduced braking power is the result.
Period. End of story. Now come all the idiots saying "but PORSCHE does it" and blah blah blah...well, they have rotors that are big enough to accept the required thermal energy and STILL be filled with holes (they're cast that way, not drilled) so they're big enough to generate the rotor torque they're looking for. Practically nobody on the street and most assuredly single-digit numbers of people with Contours have the capacity to use this effect.
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"Absolut Rara."
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"Absolut Rara."
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Originally posted by SleeperZ:
Originally posted by Rara:
Originally posted by SleeperZ:
and really high thermal expansion.
Nope, that alone would make the cracking problem worse.
I think not.
One should fully understand thermodynamics before teaching it.
With the proper alloy, a C/D rotor WITH high thermal expansion (and with the other properties I described above as well as a few I didn't describe) would expand into the holes, not outward.
This would only be possible with an alloy that would transfer heat into inner layers of the rotor, where a heat sink is mounted between the 2 sides of the rotor.
(To better understand the statement above; Think of a brake rotor as a stack of 3 pancakes, the top pancake transfers heat to the middle pancake, which inturn transfers heat to the bottom pancake. Finally the bottom pancake transfer heat to the plate. And the plate disipates the heat.)
I must ask you to follow your own advice. Keep in mind that a material with a high thermal expansion rate would be more prone to cracking at points where the thermal gradient is high, especially if a high stress concentration was at the same point, oh, something like a drilled hole would do the trick.
Also, in order to run a rotor with a higher than typical thermal expansion rate, you would have to increase your caliper seal rollback to limit serious DTV problems over time, and this would toss pedal feel and initial response right on out the window.
Further, lowering the thermal conductivity of the outer face of the rotor would limit the ability of the rotor to absorb the heat, generated while braking, fast enough, which means the temperature of the pad, caliper and fluid would increase significantly over a short period of time. This is bad. Also, if you can figure out way to vary the thermal conductivity across the depth of the rotor, fantastic, except that you have just decreased the thermal stability of your rotor, especially if you have a high thermal expansion rate, because as heat is transferred into the rotor during a braking event, you create tremendous internal stresses into the rotor itself because they will all be expanding at different rates (because of the temperature gradient during the transient event). If they existed, I wouldn't be surprised at all to see all 3 "pancakes" seperate under anything other than mild use.
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How am I weakly addressing the issue of cracking?
How am I ignoring the issue of how brakes work?
I interjected a suggestion that solves the problem of cracking and allows for maximum heat absorbtion.
A dense enough alloy with a suffecient enough thermal pass-through rate will absorb the the heat created by the friction and transfer it (at a rate greater than or equal to the rate at which it accepts it) to a heat sink in the center of the rotor that dissipates heat (at a rate greater than or equal to the rate at which it accepts it).
Most likely an alloy that absorbs heat quick enough will expand.
An alloy that only expands in a single dimension (planar expansion), not an alloy that swells (expands in all dimensions), needs to be chosen.
The expansion of the alloy can be directed inwards by adding a ring of a diffent alloy at a density and tencil strenth greater than the alloy of the rotor.
Then the rotor is given an area to expand by crossdrilling in holes.
The ring would also need to be very thermally reflective.
All I was saying, is that it's possible to make a rotor that is better when C/D than when it is not.
The cost of doing so would be great, exotic alloys would need to be used and the process directly thermal bonding two alloys even in small amounts would cost more (1" x 1" square surface area is about $2000) than most brake packages currently offered.
Knowing how brakes work, and understanding thermodynamics is two different things.
I am not telling anybody how brakes work, I am stating principles of thermodynamics (and a little bit of material science) that can be applied to braking.
Frank McCoy aka Mod-deth aka Mid Life Crisis aka SVT Doood aka mcgainer is a SCAM ARTIST
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Quote:
The cost of doing so would be great, exotic alloys would need to be used and the process directly thermal bonding two alloys even in small amounts would cost more (1" x 1" square surface area is about $2000) than most brake packages currently offered.
I love iron.
Function before fashion.
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"Absolut Rara."
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SleeperZ, I think you are missing any semblance of common sense on this one. Quote:
How am I weakly addressing the issue of cracking?
Because you haven't addressed the source of the cracking; the series of added stress concentrations through the rotor, ie the holes. At least Porsche has reasonably addressed the issue when they really want to use them, by casting the holes into the rotor.
Quote:
How am I ignoring the issue of how brakes work?
You stated that the outer layer, ie next to the pad, should have low thermal conductivity to force the heat to "flow" to the center of the rotor where it could be dissapated by the "heat sink" portion of the rotor (your use of heat sink here isn't really correct, but I'll let it go). If the outer layer has a lower thermal conductivity, then the heat isn't readily transferred into the rotor, which means it won't transfer as rapidly, which means a couple of things.
1) The heat generated at the pad rotor interface won't be absorbed as quickly by the rotor, which means it has to go somewhere during the transient event; that would be right into the pad, then the caliper, then the fluid; none of which you want absorbing the heat if you can help it.
2) If the conductivity is low, then you can pretty much kiss the outer surface of the rotor, as well as the outer third of the cross drilled holes goodbye for radiating the stored heat to the air. Especially considering you can't leave any coatings or anything on the rotor surface, becasue it would get worn away.
3) I'm sure there's more, but that's enough for now.
Quote:
I interjected a suggestion that solves the problem of cracking and allows for maximum heat absorbtion.
No, your solution would lead to additional cracking, and in additional areas and planes than before. Differing thermal properties across a rotor's thickness will lead to much higher stressed zones across the boundary layers between each region.
Quote:
A dense enough alloy with a suffecient enough thermal pass-through rate will absorb the the heat created by the friction and transfer it (at a rate greater than or equal to the rate at which it accepts it) to a heat sink in the center of the rotor that dissipates heat (at a rate greater than or equal to the rate at which it accepts it).
Now, see this is slightly different from your original proposal, now you simply refer to a "suffecient" (sic) thermal conductivity, implying a single rate, where before you proposed three different rates across the thickness of the rotor. The part that is still screwed up here though, is you make the statement that it should transfer the heat at an equal or greater rate than it received it. If you could do this, your rotors would be more or less ambient temperature regardless of the braking event. If you can figure this one out practically, more power to you. I'll tell you this, in a practical situation, you want the rotor to absorb the heat from the braking event as fast as possible, keeping as much heat out of the rest of the foundation components as possible. Then, after the braking event is done, you worry about getting the heat out of the rotor. And unfortunately, you are practically limited to ambient air as the only cooling medium (yes, liquid cooled brakes have been tried, and there is a reason they are extremely uncommon still)
Quote:
Most likely an alloy that absorbs heat quick enough will expand.
Tell you what, you find me any alloy that won't expand when temperature is increased. In all of my engineering classes, Thermo, Materials Science, etc. I don't recall a single material that had a coefficient of thermal expansion that was a dead flat zero.
Quote:
An alloy that only expands in a single dimension (planar expansion), not an alloy that swells (expands in all dimensions), needs to be chosen.
Got any guesses on any alloys that really only expand in one direction? Any that would be terribly useful here?
Quote:
The expansion of the alloy can be directed inwards by adding a ring of a diffent (sic) alloy at a density and tencil (sic) strenth greater than the alloy of the rotor. Then the rotor is given an area to expand by crossdrilling in holes. The ring would also need to be very thermally reflective.
Yup and at the same time it can dramatically increase the internal stresses of the rotor, woohoo! this is exactly what we want! MORE STRESS AT THE CONCENTRATIONS THAT ALREADY EXIST!!
btw, this rotor is getting pretty damn complicated, as I believe we are up to 4 different very fancy unobtianium alloys. On a side note, I'm not sure i would trust the design of someone that can't spell "Tensile" or "different" or "sufficient". . . (and no way can you say you fat fingered the typing on those, as none of the wrong letters are even close to each other)
And why would the ring need to be thermally reflective? So it would be colder than the rest of the rotor? So it could induce MORE thermal stresses into the mix? I'm not gonn even touch the part about the rotor expanding into the holes, since it can only locally expand into the holes, what about all the areas of the rotor that aren't right next to a hole? You would need a lot of holes; which further reduces the thermal capacity of the rotor, raising rotor temperature, which creates more stresses. It's a vicious cycle.
Quote:
All I was saying, is that it's possible to make a rotor that is better when C/D than when it is not.
I think its pretty clear that this rotor isn't better.
Hey, here's a better idea, rather than work SO hard to save your precious cross-drilling, why wouldn't you work to come up with a rotor material that lives at a much higher temperature, and then work to improve cooling airflow to that rotor? You know, kinda like Formula One does with carbon composite rotors. . .
Quote:
The cost of doing so would be great, exotic alloys would need to be used and the process directly thermal bonding two alloys even in small amounts would cost more (1" x 1" square surface area is about $2000) than most brake packages currently offered.
Hmm, wait, I have an idea, how about we just don't drill holes in the rotor in the first place? Then we can just stick with a good old cast iron plain face rotor that is dirt cheap and will have similar performance anyway.
Quote:
Knowing how brakes work, and understanding thermodynamics is two different things.
I dunno, maybe they aren't, I mean, you don't seem to have quite the grasp you need on either one. Then again, maybe they are, I didn't know nearly as much about brakes back when I was taking my thermo classes.
Quote:
I am stating principles of thermodynamics (and a little bit of material science) that can be applied to braking.
And not doing a terribly good job at it unfortunately. But keep working at it, you'll get there.
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damn, this horse died a long time ago. everyone has seen both sides so let them take from this what they want but end it already. peace.
PS: rara i asked about your twin turbo set-up in the pics and vids section. if you could go take a look. thanks.
Oo (xxx)oO
o xxxxxxxx o
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Originally posted by mikey boy:
damn, this horse died a long time ago. everyone has seen both sides so let them take from this what they want but end it already. peace.
PS: rara i asked about your twin turbo set-up in the pics and vids section. if you could go take a look. thanks.
Can cross-drill rotors be machined?
Actually, I'm rather enjoying the technical discussion, so if you can't handle it...
Function before fashion.
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LOL! Now we get right into big, fat bootylicious J-lo meaty TECH and people want to abandon the discussion to let others "take from it what they will". EXACTLY why it should go on as long as the people providing actual tech can stand banging their head against the wall. The more people that come away from this knowing more about how brakes REALLY work, the better. If you're done, then...well...buh-bye then. I'm still listening, I hope others are too.
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Oo (xxx)oO
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Your summary of the points made between Rara and Loco is more or less correct. Your conclusion about what that amounted to, however, is baseless, and your cracks about people's personality traits are completely uncalled for, and not justified by the data, because you're both painting Hector as refusing to back down from broad claims that only you put on the table, not him.
So let's try to have a bit of basic discipline and courtesy here: rule 1 being to discuss brakes rather than people, and rule 2 being to address the point the other guy actually made, instead of what you'd like to read it as between the lines. Don't those strike you as sound principles?
What everybody has learned here is that there are lots of reasons why cross-drilling is not good, and at the same time there's one solid example of some cross-drilled rotors being superior to some plain rotors. There is nothing inconsistent about both of these being true. It's no grounds whatever for making personal attacks, or even for claiming that anyone is in the wrong.
Now I still would like to know whether cross-drilling might be a good idea for long downhill descents. I'm guessing this might be one situation where they actually help, since the problem is heat accumulation over many minutes with no hard braking at any one time, so rate of cooling is more important than thermal mass. That's what I got cross-drilling for, and I still have no idea whether it helped or not.
Last edited by Paul Kienitz; 05/23/03 10:37 PM.
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ha ha ha ha don't spill your tea on your lap, Paul. This isn't a professional organization, it's an internet board. Get over yourself and don't jam your pinky too hard drinking your tea.
Now...on to you, personally. You clearly have a literary capacity far beyond your cognitive skills or you'd have GOT IT by now that the cross drilling [censored] HURTS HEAT CAPACITY, and what time would that heat capacity be taxed to its highest? Oh, maybe on a long descent, with few cooldown periods? I mean DAMN.
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Calypso Green '92 Mustang LX coupe, 13.56/101
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Originally posted by Rara:
I think that is more than plenty to show the LoCo is attributing his "fantastic" brakes to the cross-drilling on the rotors. Or at least that is what he is telling the rest of the world . . .
Nothing you quoted says that. Nothing you quoted implies that logically. Every quote you quoted just says "This brand of crossdrilled rotor is superior to stock rotors". Nowhere is the superiority attributed to the drill holes themselves. Just to the brand/model of rotor, which happens to have that feature among others.
On the 14 factors vs. two, I'll just say that the manufacturer has lots of degrees of freedom for each part but the consumer only has one, and since we're discussing consumer choices that seems to me to be the range to focus on. Which is what the rest of us have done; nobody else made special claims any more particular than the brand/model choice level.
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Originally posted by Paul Kienitz:
Your conclusion about what that amounted to, however, is baseless, and your cracks about people's personality traits are completely uncalled for, and not justified by the data, because you're both painting Hector as refusing to back down from broad claims that only you put on the table, not him.
Originally posted by LoCoz2.0:
My cross drilled rotors work tons better than the crappy stock rotors. The C/D are not warped at all. I know bigger brakes are always better but for us poor folk C/D is a good option! With all the abuse I put on my C/D...the stockers would have been garbage!
Originally posted by Paul Kienitz:
So let's try to have a bit of basic discipline and courtesy here: rule 1 being to discuss brakes rather than people, and rule 2 being to address the point the other guy actually made, instead of what you'd like to read it as between the lines.
Have you read this thread? Maybe you should start at the beginning. Rara has gone out of his way, and in lengthy detail, of brake materials--the crux of this thread!!!
Originally posted by Paul Kienitz:
What everybody has learned here is that there are lots of reasons why cross-drilling is not good, and at the same time there's one solid example of some cross-drilled rotors being superior to some plain rotors. There is nothing inconsistent about both of these being true. It's no grounds whatever for making personal attacks, or even for claiming that anyone is in the wrong.
It appears that proper research methodology escapes you. This, too, was discussed. So many factors changed in Hector's example that it cannot be relied upon. The numerous changes explained by Rara ARE IN FACT CHANGES! Small, seemingly insignificant factors, add up to very large problems. If you haven't gotten that concept by now then God help you.
Originally posted by Paul Kienitz:
Now I still would like to know whether cross-drilling might be a good idea for long downhill descents. I'm guessing this might be one situation where they actually help, since the problem is heat accumulation over many minutes with no hard braking at any one time, so rate of cooling is more important than thermal mass. That's what I got cross-drilling for, and I still have no idea whether it helped or not.
-- 1999 SVT #220 --
In retrospect, it was all downhill from here. RIP, CEG.
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Originally posted by Paul Kienitz:
Nothing you quoted says that. Nothing you quoted implies that logically. Every quote you quoted just says "This brand of crossdrilled rotor is superior to stock rotors". Nowhere is the superiority attributed to the drill holes themselves. Just to the brand/model of rotor, which happens to have that feature among others.
See my post above. You OBVIOUSLY DID NOT READ PAGE ONE! 
Originally posted by Paul Kienitz:
On the 14 factors vs. two, I'll just say that the manufacturer has lots of degrees of freedom for each part but the consumer only has one, and since we're discussing consumer choices that seems to me to be the range to focus on. Which is what the rest of us have done; nobody else made special claims any more particular than the brand/model choice level.
No, we have many choices--more than just C/D or non-C/D. Just in non-C/D there is everything from the $20 AutoZone rotor to the $100+ rotor. By choosing a vendor and price point, you are choosing material, weight, etc.--all the little things that add together for a low- quality or high-quality rotor. YOUR choice to ignore those little things by not doing research on vendors doesn't mean OUR only choice is ONE non-C/D rotor or ONE C/D rotor.
-- 1999 SVT #220 --
In retrospect, it was all downhill from here. RIP, CEG.
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Originally posted by RogerB:
1) Learn critical thinking.
2) Learn about the scientific method.
From all appearances, it certainly seems that you are attributing the results to the holes.
"Critical thinking"... my god.
Rara has emphasized that he does brakes for a living, and naturally for someone in that position it's painful to see what seems to be misinformation. Well, I do logic for a living. And seeing misuses of logic like this -- insisting someone is clinging to a given idea even though (a) none of his words actually say so and (b) he's explicitly disavowed the idea being attributed to him... well, that gives me a pain in the same part of my being that hurts Rara if someone thinks cadmium plating shortens stopping distances.
This reminds me of an email debate I got into over the war in Iraq. The other guy kept coming back to an idea that I must hate America. I don't, of course, yet no matter how much I explain that I object to only to certain specific policies, he still thinks it's all proof that I hate America. It was like having someone constantly insist that you must be gay when you know you're not. We can avoid this kind of crap if we just grant the other party the basic respect of assuming that he knows what his own position is, and if he says it's X, then it's X, and it's not your place to claim he really must have meant Y.
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Nobody's CLINGING to the idea that he hasn't disavowed his belief, all this last several pages has been trying to explain to YOU where the idea came from in the first place while you argue that it never should have been. GawdDAMN you are dense.
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Originally posted by MFE:
You clearly have a literary capacity far beyond your cognitive skills or you'd have GOT IT by now that the cross drilling [censored] HURTS HEAT CAPACITY,
Where did I ever suggest it didn't?
Originally posted by MFE:
and what time would that heat capacity be taxed to its highest? Oh, maybe on a long descent, with few cooldown periods? I mean DAMN.
Heat capacity is taxed to its highest on hard stops from high speed. Heat dissipation is taxed to its highest on long downhills. When you're talking about gentle braking continued for an hour, you can't treat the rotor as something that just absorbs heat and gets linearly hotter the longer you brake, as you can in short stops. You have to talk about the equilibrium point where heat flow in = heat flow out. The capacity for heat stored inside the rotor doesn't change that equilibrium point, it only changes the time it takes to reach equilibrium.
Nothing anyone has said is addressing this side of the question, which is why I'm still as in the dark about it as I was six months ago.
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Originally posted by bigMoneyRacing:
It appears that proper research methodology escapes you. This, too, was discussed. So many factors changed in Hector's example that it cannot be relied upon. The numerous changes explained by Rara ARE IN FACT CHANGES! Small, seemingly insignificant factors, add up to very large problems. If you haven't gotten that concept by now then God help you.
Dude, NOBODY SAID OTHERWISE. That was my point, that someone was trying to make a claim about "this model of rotor" into a claim about "this one feature of the rotor", when all of us knew perfectly well it was not the only difference and never said it was.
Originally posted by bigMoneyRacing:
Originally posted by Paul Kienitz:
Now I still would like to know whether cross-drilling might be a good idea for long downhill descents. I'm guessing this might be one situation where they actually help, since the problem is heat accumulation over many minutes with no hard braking at any one time, so rate of cooling is more important than thermal mass. That's what I got cross-drilling for, and I still have no idea whether it helped or not.
You lecture me about "research methodology" and then, as soon as I raise a real tech question, it goes completely over your head? Is that what "" means? haha
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Oh my God, you people are unbelievable. So who's got the smaller and faster sports car?
All of this could have been avoided (but at the expense of a really good discussion about thermal temps for rotors) if Rara would have pointed out that Hector saw a marked improvement because it was a performance rotor over an OEM. Unless I am missing the point here as well (it's been known to happen from time to time). Hector also mentioned that the bigger rotor would have been a better idea if you are going to go c/d. Great suggestion to do the experiment with solid vs. c/d under the same conditions, but we know the answer to that already due to this thread and previous threads in this forum. As for Hector spreading BS..well not really. There are many many people spreading BS and he is talking c/d for street conditions and his experience--not saying go out and buy some. Rara has already stated that they should not be used for racing, and from what I gathered are mainly for looks on street cars. MFE, no one has let the issue go so you're a pot calling a kettle black on an "internet board." It's hard to take a joke, though, when you get beat up on sometimes, ya know. No one likes to be called "dumb". "Dumb" is not productive in a conversation filled with really good information. Combine that with what happens when you attack people on the board and the thread goes to sh*t and all the good info is overlooked because of the name calling and bickering about who said what.
Rara, Paul, Sleeper, some really good information about rotors. I have been talking about this with a guy from work, and now have something to contribute to that conversation for next week. My .02 has been brought to you by the letters "P" and the letter "W" Carry on...
Mighty Mouse strikes again
Last edited by LoCoChick'95; 05/24/03 01:41 AM.
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I've got mods.
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Originally posted by Paul Kienitz:
Originally posted by RogerB:
1) Learn critical thinking.
2) Learn about the scientific method.
From all appearances, it certainly seems that you are attributing the results to the holes.
"Critical thinking"... my god.
Rara has emphasized that he does brakes for a living, and naturally for someone in that position it's painful to see what seems to be misinformation. Well, I do logic for a living. And seeing misuses of logic like this -- insisting someone is clinging to a given idea even though (a) none of his words actually say so and (b) he's explicitly disavowed the idea being attributed to him... well, that gives me a pain in the same part of my being that hurts Rara if someone thinks cadmium plating shortens stopping distances.
This reminds me of an email debate I got into over the war in Iraq. The other guy kept coming back to an idea that I must hate America. I don't, of course, yet no matter how much I explain that I object to only to certain specific policies, he still thinks it's all proof that I hate America. It was like having someone constantly insist that you must be gay when you know you're not. We can avoid this kind of crap if we just grant the other party the basic respect of assuming that he knows what his own position is, and if he says it's X, then it's X, and it's not your place to claim he really must have meant Y.
You forgot to read this part of my quote:
Quote:
If you weren't then you would say something like, "My stock replacements warped, but my KVR's didn't." Instead, you stress over and over how they are crossdrilled. Language is a funny thing.
Sure enough, he says C/D over and over and over. If he didn't mean that, well, then he shouldn't have said it. And he hasn't disavowed it. He has said "It's just my opinion." Or, he has said things like, "I never said that."
I do logic for a living, too, and I must say that comparing a technical disagreement to a political disagreement is pretty pathetic in the relevant analogy department.
Now, if Hector understood critical thinking, he would never say half the crap he has said about how great crossdrilling is (despite all evidence to the contrary.) If he has changed his mind, great. If not, so what. You can't save everyone.
Oh, I've read the whole thread, BTW, but as I said, I really don't recall any "disavowal" by Hector. If you care to present it, I will readily admit my error. That's called honor. Something else that seems in short supply these days.
Function before fashion.
'96 Contour SE
"Toss the Contour into a corner, and it's as easy to catch as a softball thrown by a preschooler." -Edmunds, 1998
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Since I easily loose arguments with myself, all I like to add is thanks to RogerB for sharing the URL's. The Stop Tech's articles has cleared up allot of myths I've heard over the years. A now retired engineer once told me, he never would comment on any technical issue that he himself hadn't run tests/R & D. And one other scarey issue, the more I learn the more I realize I don't know. i.e. "always keep an open mind" TNX Paul holes is current flow---right?
Paul
98 Mystique LS 2ea (07/97)(08/98)
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Originally posted by F111D F:
Since I easily loose arguments with myself, all I like to add is thanks to RogerB for sharing the URL's. The Stop Tech's articles has cleared up allot of myths I've heard over the years.
A now retired engineer once told me, he never would comment on any technical issue that he himself hadn't run tests/R & D.
And one other scarey issue, the more I learn the more I realize I don't know. i.e. "always keep an open mind"
TNX
Paul
holes is current flow---right?
It's good that someone got something out of this thread. I thought the bickering here was a waste of bandwidth. Maybe it wasn't after all.
Jim Johnson
98 SVT
03 Escape Limited
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This is the biggest flame fest I have ever seen!!! At least the stoptech articles made it in. . . .
#4559 of 6535 born on Feb 17, 1998
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"Absolut Rara."
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Originally posted by Kingpin:
This is the biggest flame fest I have ever seen!!! At least the stoptech articles made it in. . . .
You're kidding right? Very very little flaming going on here. What you see is a warm technical discussion.
I can't stand the "why can't we all just get along" sentiment; I stand firm in the old school "let's hash it out until its right".
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Oh by all means dont get along, I have learned more about brakes than ever in this post. Well at least enough to hold my own when someone starts talking about brakes. And I will say, I have been quite entertained in the process!
#4559 of 6535 born on Feb 17, 1998
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As long as people are learning it's never a waste of bandwidth. I'm glad to see that logic rears it's head. Often times it gets pushed aside in the rush to "upgrade" our cars.
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Originally posted by MFE:
Brakes work by converting kinetic energy to heat energy through the use of friction.
The more heat energy the rotors can accept, the more braking power you have.
Cross-drilling reduces mass more than they add cooling capacity thanks to the holes.
Reduced mass means reduced heat sink.
Reduced heat sink means the rotors can't accept as much heat energy. Therefore reduced braking power is the result.
Actually once brakes have absorbed heat from the initial braking, the ability to transfer thermal energy away from the brake to the air becomes the limiting factor. The heat capacity of the rotor becomes a minor effect.
Properly designed hollow rotors have more than twice the radiating area of solid disc rotors. This has resulted in the trend toward hollow vented rotors in the past decade despite increased manufacturing difficulties and costs.
Cross drilling and slotting of rotors is a doubled edged sword. Most of the problems with rotor cracking with drilled rotors relate to the quality of the drilling or machining job.
If the cross drilling is done in a manner where problems are created in the rotor, then cracking may occur. Problems include:
1/ the holes intersect cross webs,
2/ excess heat is generated from too fast of a machining process or lack of a cooling fluid during drilling,
3/ stress is trapped in the rotor and distortion occurs from excessively fast drilling,
4/ microcracks form during a poorly controlled drilling process, or
5/ sharp edges are left at the hole corners that lead to stress cracks. After drilling the corners should be radiused or chamfered to remove sharp corners.
If any of the conditions above happen it would not surprise me if rotor cracking occurs.
At the other extreme, rotors made from quality materials can be machined using best practices, annealed after machining and a light cut taken on the wear surfaces. I would expect cracking of these rotors to happen with a very small occurance rate.
If you know what you are doing you can carefully machine the surface of drilled and slotted rotors, chamfer the corners and avoid problems.
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All this sounds great. Now show me the shop or machine that radius's the holes after they are drilled. Oh, not the outside of the hole, we see that part, but rather the INSIDE of the hole where the venting or vanes are.
Your comments are valid in many ways, but drill a cast iron rotor and subject it to abuse equal to that of an undrilled one and it'll crack much sooner.
For you guys with them, just keep and eye on the holes once in a while and replace them. That's all is needed. Wait for large cracks and it's trouble.
Bottom line: buy what floats your boat and live with it.
Last edited by Todd TCE; 05/31/03 12:00 AM.
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"Absolut Rara."
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Couldn't have said it any better myself Todd.
Though, I disagree with Jon in some ways.
First, heat capacity is always important, whether its your first stop or your fifth stop. How much heat your rotor can absorb is key because heat is generated extremely quickly while stopping, and you tend to have much much more time to dissapate the heat to the air after the stop.
Also, while the items you list will reduce the cross-drilled rotors tendancy to crack, it does not eliminate the source of the cracks, the stress concentration created by the drilled hole. Cracks are still likely to happen far more regularly than on a solid faced rotor (ie not drilled).
The best solution I have seen for rotors with holes, is some of the very high dollar Porsche rotors, where the holes are cast into the rotor rather than drilled. Though, if you notice, you very rarely see even these rotors on the serious Porsche race cars.
Honestly, the best application for drilled rotors I know of, is motorcycles. Bikes typically use a solid rotor(s) in the front of very large diameter (relative to the wheel size, when compared to car packages). Now on a bike, the rotational inertia of the wheel/tire/rotor plays a HUGE part in the steering feel and responsiveness, so the rotors are drilled to save weight and improve steering feel on the bike. And the heat capacity of the very large rotor(s) is such that the loss due to drilling has little to no effect on performance.
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How important is heat capacity? How much mass do you remove when drilling and machining a rotor? I would estimate about 2% or a bit less based on rotors I have machined and drilled. You also remove a similar amount of material when resurfacing rotors
dQ = Cp*m*dT where:
dQ = heat input,
Cp = heat capacity of a material
m = mass of material being heated
dT = temp rise
The equation can be rewritten:
dT = dQ /(Cp*m)
Assume dQ and Cp are constant and dQ results in a temp rise of 600F from 100F to 700F for an undrilled rotor. If you reduce the rotor mass by 2% you get a 612F rise.
I agree that rotors have to be corectly sized to the mass of the vehicle. However, the reduction in heat capacity by drilling a correctly sized rotor in insignificant.
Do you really think an additional temp rise of 12F is going to make a significant difference? If you removed 25-30% or more metal from the rotor, you might see some effect from lost heat capacity, but this will involve more than just drilling the rotors.
Assuming that everyone here is using brake pads with an epoxy or polyimide binderm I used 700F as my example for a continuous use temp. If you wanted to be optimistic 900F could have been taken as an upper limit. If you see rotor temps much above this you will need to go to sintered metal or carbon-carbon pads or you will overhat the pads.
Don't limit yourself to what happens after one or two hard stops. Consider the vehicle dynamics at a NASCAR short track or a road course such as Lime Rock or Watkins Glen. The brakes must disappate heat for hundereds of barking cycles over a 100-500 mile race. Clearly heat disappation not heat capacity (as long as the brakes are properly sized) is the most critical factor.
The better race shops use sufficient cutting fluid to cool the rotors during machining and heat treat the rotors afterward to remove stress. Usually a very light resurfacing at low speed and low pressure is used to true the rotor surface after heat treat. I've had this done on about 6 pairs of rotors and never had one crack.
One thing you must watch out for on the street is stress induced corrosion. Machined rotors do have greater opportunity for corrosion problems over undrilled rotors.
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Jon,
Heat capacity is important because if dQ exceeds Cp at any point during the very short period of time of a brake application, all of that excess heat has to go somewhere, and it obviously isn't into the rotor. Also, while total heat capacity may be constant, available heat capacity is ever changing, so for a dynamic system, it is not safe to assume Cp is the same at any given moment. And as to your mass assumption of 2%, I will leave it be, simply because I do not wish to calculate it at the moment. Perhaps if I get bored at work tomorrow, I will run through it . . .
The real point is the stress concentration induced by the holes themselves. You can apply any process you wish to minimize the stress induced from machining, etc., but the fact remains that simply by the presence of the hole (or absence of presence?) you have introduced a geometric stress concentration into the rotor that you cannot eliminate by any method you can name, aside from not making the holes in the first place. Further, if they work as well as you claim in aiding heat dissapation, then you are also inducing significant thermal stresses in the rotor as well.
Further, we are not talking about competition use here anyway, I have conceded that there are some specialized situations where cross-drilling is more beneficial than detrimental, and all situations where that applies, excluding street-driven motorcycles, is in competitive motorsport.
I do not dismiss the importance of dissipating the heat in the rotor, but how much can the holes actually improve heat dissapation? Sure you increase the surface area, but where? Not in the prime spots of cooling airflow, and perpendicular to the direction of the normal flow. I believe at best they would be turbulence generators for existing cooling air flow. Heat dissipation depends on airflow, and lots of it, over the rotors, and through the open center section of a vented rotor, the holes don't do anything to increase the amount of airflow, and the additioanl srface area they do provide, isn't in the best place to make use of the existing airflow anyway.
If you are really having that much of a heat dissipation issue in a given application, rather than make your rotors weaker, I would recommend improving the brake ducting.
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Now that this has gotten back to some reasonable conversation....
My personal opinion is that it's less the loss of mass that adds to the problems but rather the huge difference in temps that the rotors see when drilled rotors are exposed to high temps and ambient air. Consider the 900 degree rotor that has 70 degree air passing over the holes. This makes for some really difficult tasks on the part of the iron to expand and contract. And if anyone thinks that they don't move that much consider the value of floating rotors in extreme applications for much the same reason.
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Originally posted by Rara:
Jon,
Heat capacity is important because if dQ exceeds Cp at any point during the very short period of time of a brake application, all of that excess heat has to go somewhere, and it obviously isn't into the rotor. Also, while total heat capacity may be constant, available heat capacity is ever changing, so for a dynamic system, it is not safe to assume Cp is the same at any given moment. And as to your mass assumption of 2%, I will leave it be, simply because I do not wish to calculate it at the moment. Perhaps if I get bored at work tomorrow, I will run through it . . .
I'll get back in more detail later, but it sounds like there is a limited understanding of thermodynamics or materials in this discussion.
"Heat capacity is important because if dQ exceeds Cp at any point during the very short period of time of a brake application, all of that excess heat has to go somewhere"
dQ is in units of cal/sec or joules/sec depending on whether you are using English or scientific units. Cp is in cal/(deg-F - lb) or joule/(deg-K - g). The total heat capacity of of an object is Cp*m. I don't know how you compare dQ to Cp to determine if one exceeds the other
"all of that excess heat has to go somewhere, and it obviously isn't into the rotor"
Some of it is into the brake pad and calipers. for obvious reasons you have to limit this to avoid overheating the pads.
Besides transferring the braking energy as heat, there are a limited number of ways you can extratct heat from the brakes. Heat can conduct through the brake pad and caliper and eventually heat the surrounding air and structure, it could be transformed into acoustical energy, or you could spray water on the rotor. The resulting evaporation of water will carry heat away very effectively. If you want to get complicated you could magnetically couple the rotor to another structure, however the hardware to do so would be heavier than the brakes. Do you know of another way that heat could be disappated from the rotors?? In any case the mechanism should be measurable given the large amount of heat genereated by braking.
So where do you think all the excess heat is going? Perhaps it is being dissapated from the rotor to the air via infrared radiation. Hot objects have very distinct infrared signatures.
"Also, while total heat capacity may be constant, available heat capacity is ever changing, so for a dynamic system, it is not safe to assume Cp is the same at any given moment. "
Over a finite temperature range Cp changes very little (less than 1-2% over a 100F range) unless a phase change occurs. One example of a phase change is melting... I'm sure no one here wants to even get close to the melting pont of the rotors. (2500-2700 F)
I've studied the thermal characteristics of materials for over 25 years. There are no surprises with ferrous materials such as steel, cast steel and cast iron in the room temp to 1200F range. Tempering is usually done in the 400-1550F range with melting in the 2500-2700F range. Internal phase changes (going from martensitic to austenic phases in steel, as an example) do slightly alter the Cp, but once a part is at equilibrium the Cp is continuous with a very flat slope over the entire RT to 1200+ F range.
Assuming a phase change doesn't occur 'all that excess heat' just results in more temperature rise, dT. It doesn't magically do anything else. It could melt the brake pads or boil the brake fluid to disappate excess heat. However, I think we are trying to avoid those scenarios.
I stand by my original statement, if you reduce the mass of a rotor by 2%, expect dT to increase by 2% assuming the same heat input, dQ.
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Quote:
I'll get back in more detail later, but it sounds like there is a limited understanding of thermodynamics or materials in this discussion.
No, the difference is I'm looking at it from a practical system level.
Quote:
dQ is in units of cal/sec or joules/sec depending on whether you are using English or scientific units. Cp is in cal/(deg-F - lb) or joule/(deg-K - g). The total heat capacity of of an object is Cp*m. I don't know how you compare dQ to Cp to determine if one exceeds the other
Again, I am looking at it in a practical system level, I didn't think I had to be overly explicit here, I thought you were intelligent enough to figure it out. You have situation where a stop has a rate of heat input over time of dQ, and a time of S; using those two parameters, you can calculate a total amount of heat into the system. Then, since your rotor will not appreciably change mass during a stop (unless your cross-drilling causes a catastrophic failure) m will be constant, so Cp*m doesn't change either. Now, the system will have a temperature at which it no longer functions adequately, typically limited by the pad material, or by the brake fluid boiling in the lines, but there is some temperature for a given system at which "fade" sets in.
This means, that for a given system, there is only a certain amount of Q that the rotor can absorb before the system goes over that temperature, typically in the neighborhood of 700 deg F for a street pad.
With regard to Cp changing, again, I was oversimplistic. Cp itself does not change, but the amount of available heat capacity of the rotor at any given time depends on the temperature of the rotor, and the difference between that temperature and the maximum temperature at which the system can adequately operate. Again, my problem for using the term Cp incorrectly, but my intent should have been obvious. In my defense, I posted that late at night, and I've been sick.
Quote:
I stand by my original statement, if you reduce the mass of a rotor by 2%, expect dT to increase by 2% assuming the same heat input, dQ.
I don't argue your calculations on this, I even verified the 2% on a typical rotor. Just remember, the heat is also going into the pads and the caliper at the same time, and at likely a very different rate (Cp will be different, as will mass). Its just that the temperature of the rotor isn't the real problem, because as you state, there are no surprises even in to the 1200 deg F range, its in the pads and fluid where you have to be very careful about the heat. The rotor is a heat sink for them, and as such, should have as much heat capacity as possible to avoid excess heat into the pads, calipers and fluid. Once also must consider that OEM rotors are designed pretty much right on the edge of required thermal capacity for meeting the Federal FMVSS135 stopping requirements, so 2% could in fact make a big difference on an OEM rotor design.
And once again, I must point out, that you are still missing the main importance of why cross-drilling is bad; the geometric stress concentrations introduced into the face of the rotor, and then compounded by the thermal issues associated with dissimilar cooling at the holes. These rotors tend to crack, that's all there is to it. Any percieved improvements in cooling performance cannot offset the added danger associated with having rotors that tend to crack and fail. Granted, light use on the street will not likely induce cracking except over a long period of time, but honestly, how many of us are really easy on our brakes? Cross-drilling was originally intended to allow an escape path for gases generated by older type pad materials under heavy use. "Out-gassing" of pads is not a problem with modern pad materials, so the original function of the holes is no longer existant, and yet they remain for their "bling factor". Which is fine, as long as people understand the ramifications of enjoying the "bling factor".
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Originally posted by Rara:
I do not dismiss the importance of dissipating the heat in the rotor, but how much can the holes actually improve heat dissapation? Sure you increase the surface area, but where? Not in the prime spots of cooling airflow, and perpendicular to the direction of the normal flow. I believe at best they would be turbulence generators for existing cooling air flow. Heat dissipation depends on airflow, and lots of it, over the rotors, and through the open center section of a vented rotor, the holes don't do anything to increase the amount of airflow, and the additioanl srface area they do provide, isn't in the best place to make use of the existing airflow anyway.
Intuitively it seems to me that the holes would tend to act as an inlet to the central venting, and that if the rotor is spinning at a decent speed the center vents will produce a bit of a vacuum that would pull air in through the holes. Wouldn't this contribute some cooling?
(Remember that the reason I tried cross-drilled rotors was for mountain descents, in which heat capacity is of minimal importance but dissipation is all-important. Under these conditions there are no individual hard stops, but heat may accumulate steadily over as long as an hour. My last two imports had no trouble with this but the tour overheats badly.)
Originally posted by Rara:
If you are really having that much of a heat dissipation issue in a given application, rather than make your rotors weaker, I would recommend improving the brake ducting.
What sort of ducting might help if the speed at which one is doing this braking is only like 35 MPH? Is ducting useful then?
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Quote:
Intuitively it seems to me that the holes would tend to act as an inlet to the central venting, and that if the rotor is spinning at a decent speed the center vents will produce a bit of a vacuum that would pull air in through the holes. Wouldn't this contribute some cooling?
Not nearly as much as you think. A vented brake rotor works much like a centrifugal air pump, as the rotor spins, it creates low pressure areas behind the vanes, and air is drawn in from the center of the rotor to fill that low pressure area. So basically air is pumped from the center of the rotor radially outward (this is why you direct the ducting to the center of the rotor, for it to pick up the colder air, though, because the contour is vented on the outer face at the center, its a bit tough). When you drill holes in the face, it takes a lot away from the centrifugal pump effect by not allowing the low pressure area to build up nearly as effectively.
And proper ducting is always useful, well, as long as you are moving anyway.
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Originally posted by Rara:
And once again, I must point out, that you are still missing the main importance of why cross-drilling is bad; the geometric stress concentrations introduced into the face of the rotor, and then compounded by the thermal issues associated with dissimilar cooling at the holes. These rotors tend to crack, that's all there is to it.
I'm not missing your point. I fully understand the issues with stress in materials and the effect of geometry. I've worked as a materials scientist for over 30 years and with materials & structural engineering for the last 25 years. Aircraft disc brakes and very large elevator disc brakes are just two of the many components I've had fun working with.
The problem with drilled brakes is not primarily due to the geometry, but what happens during the machining process. The geometric problems are no more severe than the geometric effects and subsequent stress distribution during heating that result from th webbing.
The problem with cross drilling is what happens from the microscopic to local levels, if the drilling is not done correctly. If the machinist uses a less than sharp drill bit, works too fast and does not use cooling lubricant damage can be done to the metal. The two major problems are that significant stress is left in the metal surrounding the holes and that a lot of microcracks can form in the metal.
However, if the machinist uses a sharp tool with lubricant, uses a slow feed rate and if the rotor is heat treated after machining the risk of cracking is very small.
This is an example of a layman looking at a cracked brake rotor and concluding that the drilled holes were the cause of cracking. An experienced engineer looks at a cracked rotor, analyzes the problem two levels deeper and determines the machining process was at fault. The layman concludes that drilled rotors are bad, while the engineer figures out how to properly manufacture a machined brake rotor.
Originally posted by Paul Kienitz:
(Remember that the reason I tried cross-drilled rotors was for mountain descents, in which heat capacity is of minimal importance but dissipation is all-important. Under these conditions there are no individual hard stops, but heat may accumulate steadily over as long as an hour. My last two imports had no trouble with this but the tour overheats badly.)
Paul -- if you are experiencing severe fade during mountain descents, it is likely that overheating of the pads is the root cause of fade. Using stock drilled rotors will only help a small amount with stock pads. I would suggest that you look for pads that start to fade 100-200F higher in temp. If that doesn't work, unfortunately the next step would be larger diameter rotors and pads with a larger surface area, also selecting premium pad materials. You need to spread the heat generating surface over a larger area and increase the ability of the rotor to dissapate heat. A larger caliper structure will also help increase heat dissapation though that path.
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Originally posted by JonsZX2SR:
This is an example of a layman looking at a cracked brake rotor and concluding that the drilled holes were the cause of cracking. An experienced engineer looks at a cracked rotor, analyzes the problem two levels deeper and determines the machining process was at fault. The layman concludes that drilled rotors are bad, while the engineer figures out how to properly manufacture a machined brake rotor.
That layman Rara Are you aware that not everyone is a High School Senior with a used Contour? You aren't the only engineer here. PLus, there are plenty of sites (Brake MFG's) that explain the effect CD has on brakes with the "Engineering Explanation" and feel it is not desirable.. FWIW, I have a BSME and MS myself, so I am a layman too.
So, where do you get "properly" cross drilled rotors?
Even Porche has problems with cast-in holes cracking.
Stress concentration is a problem. You can minimize it, but not eliminate it.
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My point is not that stress concentrations don't exist but that they can be minimized to a point where other things become a problem. If you only wanted to minimize stress concentrations, you would run solid rotors and avoid the stress concentrations caused by the manufacturing process and the geometry of the webs in a hollow vented rotor. Since people successfully run hollow discs, the small effect of increase stress concentration is more than offset by the advantages of hollow disc rotors.
My rotors are machined at a local shop that has done contract work for the corporation I work for. The shop has world class equipment for doing aerospace work. Sometimes I do the machining myself at the shop after hours. The rotors are heat treated after machining based on the work I've done over the past 25 years. A very light final cut is taken on the rotor faces after heat treating, to true up the faces.
The quality of work is nothing I would consider special, anything a first class race team or someone working in the aerospace field could do. I have never had a rotor crack. If I see signs of significant corrosion or damage around one or more holes after a few years I may decide to replace the rotor.
Much of what I learned over the years was from deliberately machining or processing parts incorrectly to determine the effect of poor manufacturing. If there is a way to manufacture a part so it will fail, I have probably done so. The knowledge has been applied to learning how to make parts that don't fail, regardless of whether they are aerospace, elevator/escalator or my own automotive components.
I'm sure that there are many educated and experienced people on this board, such as yourself. My intent was to share that the manufacturing process can significantly affect the durability of a component. The same design can be robust or fail depending on how it was manufacturered.
I get the impression that some people here are not interested in information that conflicts with their opinions. At the risk of getting flamed, I don't plan to contribute any further to this discussion. Different people have different opinions and each of us needs to get the job done the best way they know how.
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Originally posted by Rara:
Quote:
Intuitively it seems to me that the holes would tend to act as an inlet to the central venting, and that if the rotor is spinning at a decent speed the center vents will produce a bit of a vacuum that would pull air in through the holes. Wouldn't this contribute some cooling?
Not nearly as much as you think. A vented brake rotor works much like a centrifugal air pump, as the rotor spins, it creates low pressure areas behind the vanes, and air is drawn in from the center of the rotor to fill that low pressure area. So basically air is pumped from the center of the rotor radially outward (this is why you direct the ducting to the center of the rotor, for it to pick up the colder air, though, because the contour is vented on the outer face at the center, its a bit tough). When you drill holes in the face, it takes a lot away from the centrifugal pump effect by not allowing the low pressure area to build up nearly as effectively.
And proper ducting is always useful, well, as long as you are moving anyway.
What he said. "Intuitively," it seems to me that drilling holes in the rotor for extra cooling is like drilling holes in the water pump for the same reason.
With solid discs, your intuition is more accurate, but with modern, vented discs... well... what Rara said.
Function before fashion.
'96 Contour SE
"Toss the Contour into a corner, and it's as easy to catch as a softball thrown by a preschooler." -Edmunds, 1998
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First of all, Jon, thanks for the extra info. Too bad your feathers got ruffled, but remember that you fired the opening shot with your "layman" comment. (I would be classed as such a layman, but some of the other people in this thread would not.)
Anyway, to sum up for those of you joining late:
1. Cross-drilling has no known performance benefit with modern braking systems, and may even detract from braking performance by a) reducing heat-sink mass and b) reducing cooling airflow through the vanes.
However,
2. It is possible to resurface (machine, turn, etc.) them with the proper technique.
3. They may be more prone to cracking, but
4. The manufacturing process has a lot to do with that. IOW, not all cross-drilling is created equal.
5. A lot of people still think they look cool.
Function before fashion.
'96 Contour SE
"Toss the Contour into a corner, and it's as easy to catch as a softball thrown by a preschooler." -Edmunds, 1998
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you guys are retarded. chris was just trying to tell people that if they have the rotors they can be machined. Who cares if there is no improvement in braking. It doesnt make the car brake any worse and they look nice. I never bought mine but the previous owner did had them installed. They were machined without a problem. You guys start the same argument about this crap every week.
1998 SVT #95: Toreador Red - SHM headers, SHM custom tuned chip, K&N Filter, Energy Suspension MM inserts, Cross Drilled Rotors,Redline Tranny Fluid, Custom Billet Aluminum Shift Knob, Edelbrock RPM 5503 resonator,15.441 @ 91.66 mph
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Originally posted by SVT#95:
you guys are retarded. chris was just trying to tell people that if they have the rotors they can be machined. Who cares if there is no improvement in braking. It doesnt make the car brake any worse and they look nice. I never bought mine but the previous owner did had them installed. They were machined without a problem. You guys start the same argument about this crap every week.
Although perhaps it happened in the wrong thread I would be hard pressed to say this conversation has been "retarded".
I have learned more about brakes in reading through these many pages then I have in my previous 23 years of existence on this planet. I would say that is one of the most informative CEG threads I have ever come across.
For your comment you get this:
"Cobb - It's not just for corn anymore!"
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I think this is one of the most informative threads also. All I am saying is that this argument about cross drilled vs. slotted vs. stock must have been brought up a 1000 times by now. I posted almost a year ago that my rotors were machined without a problem. Chris is just restating this but anytime someone brings up anything about cross drilled rotors the same argument pops up again and again. If anybody wanted to know about performance of cross drilled vs. slotted vs. stock then all they have to do is a search. there will be a ton of results for them to search through. But to post the same facts every post about drilled rotors just gets rediculous.
1998 SVT #95: Toreador Red - SHM headers, SHM custom tuned chip, K&N Filter, Energy Suspension MM inserts, Cross Drilled Rotors,Redline Tranny Fluid, Custom Billet Aluminum Shift Knob, Edelbrock RPM 5503 resonator,15.441 @ 91.66 mph
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How hard is it to not look at the thread? Its not like people are sitting on your front lawn arguing about it....its the internet. Anyhow....thanks for the good brakes information guys. Cross drilled rotors are definately never coming close to my car.
"Cobb - It's not just for corn anymore!"
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"Absolut Rara."
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"Absolut Rara."
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Originally posted by JonsZX2SR:
I get the impression that some people here are not interested in information that conflicts with their opinions. At the risk of getting flamed, I don't plan to contribute any further to this discussion. Different people have different opinions and each of us needs to get the job done the best way they know how.
Jon,
I take offense at that. You as an engineer should understand the concept of hashing out a technical discussion better than most here. Can you tell me that you have never had a technical disagreement with another engineer? and further that you have never discussed it? Your only risk of getting flamed is for being a pansy and walking out just when the technical discussion is getting good. "Iron sharpeneth Iron . . ." This sort of debate is how the knowledge base of the CEG community is increased, at least for those willing to read and learn and not piss and moan about "can't we all just get along?" (Yeah, that was aimed at you SVT#95, and others like you)
Fwiw, I am in fact a degreed engineer as well, and I actively work in the automotive brake area. Does that mean I know all and can nail every single detail related to brakes? No, certainly not, but it does net me some credibility, just as your manufacturing experience does for you, and others have thier own education and experience in areas applicable. And I expect all who can add something to this technical table to do so, as a benefit to all of us. I absolutely love to see some actual tech come to this board, rather than the typical "that looks tite, Yo!" So common on boards like this. I love it when people like Todd TCE come here; a vendor that won't just spout BS to make a buck, but will disseminate REAL technical advice to his potential customers. I love to see folks like you (Jon) on here, that will actually engage in a public technical discussion that will benefit all willing to read and learn, regardless of thier experience level, or education (assuming the minimum of being able to read and operate a PC ) I'm so sick and tired of BS tech propogated by ignorant fools regurgitating what they read on a sales brochure for something from APC products or the like; let's try to get some real tech out there for those willing to learn!!!!
I'm really sorry for my rant, but I hate to see someone just give up on something worthwhile, just because someone disagrees with them. Disagreement does not mean hatred, I wish people would get that through thier thick skulls; Most of the world's greatest discoveries only happened because someone disagreed, and didn't play the "can't we all just get along" game.
All that said, you will notice, I never disagreed with your comments on the manufacturing process. In fact I think you are right on about them. I honestly was taking the initial assumption that satisfactory manufacturing processes were used in manufacturing the cross-drilled rotors we are discussing, and that additional stresses were not "processed" into them.
I still maintain that the geometric discontinuities, especially when combined with thermal issues caused by the dissimilar cooling around the holes, are enough of a stress concentration to make cross-drilling a bad idea in all but the most specialized applications. Combine that with the poor manufacturing techniques you describe, and you create downright dangerous parts.
I can find numerous photos of cross-drilled rotors, that were manufactured to satisfactory levels that still have failed under use (or at least started to fail). I seem to recall even seeing photos of failed porsche "holed" rotors due to cracking around the cast-in holes.
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Originally posted by JonsZX2SR:
Paul -- if you are experiencing severe fade during mountain descents, it is likely that overheating of the pads is the root cause of fade.
Or ultimately, overheating of the fluid, through overheating of the calipers, through overheating of the pads.
I've got 500 degree fluid in there but I've still overdone it once or twice.
Originally posted by JonsZX2SR:
Using stock drilled rotors will only help a small amount with stock pads. I would suggest that you look for pads that start to fade 100-200F higher in temp.
I currently have the KVR carbon fiber pads and for next time have been attracted to the glowing reports about Bendix titanium.
Originally posted by JonsZX2SR:
If that doesn't work, unfortunately the next step would be larger diameter rotors and pads with a larger surface area, also selecting premium pad materials. You need to spread the heat generating surface over a larger area and increase the ability of the rotor to dissapate heat. A larger caliper structure will also help increase heat dissapation though that path.
Another question which I've been asking about, and nobody has yet produced an answer to, is whether Focus SVT rotors will fit, with stock Tour calipers, inside an E0 SVT 16" rim. Apparently it's close; either barely fits or barely doesn't.
Of course, using these rotors would require me to either get a different spare, or always keep drum brakes in the back and deal with front flats by moving a rear wheel forward.
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Originally posted by Rara:
And proper ducting is always useful, well, as long as you are moving anyway.
So what does proper ducting consist of -- is it basically just a pipe that scoops up air from the front and feeds it to the middle of the rotor? Could I fake it with dryer hose?
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"Absolut Rara."
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Originally posted by Paul Kienitz:
Originally posted by Rara:
And proper ducting is always useful, well, as long as you are moving anyway.
So what does proper ducting consist of -- is it basically just a pipe that scoops up air from the front and feeds it to the middle of the rotor? Could I fake it with dryer hose?
People have done exactly that . . .
I'll see if I can dig up some pics of what some Mustang folks have done. Or maybe MFE will post up some pics of his setup on his mustang.
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Originally posted by RogerB:
and b) reducing cooling airflow through the vanes.
Well actually, it was pointed out that they would reduce airflow from the center, because they reduce the centrifugally created vacuum, and the way they reduce vacuum is by letting more air in. So the worst case scenario is that the airflow is moved, not reduced. So on that it's probably pretty much a wash.
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Considering all the info here, I agree it's too bad some opt out for reasons I don't fully understand.
To cover a few things that have been mentioned here however...
The brake torque of the wheel is controlled by the diameter of the rotor, the amount of pressure delivered to the pad and the pads Cf.
That being said, the comment I made is that if you 'over rotor' (diameter not thickness) will increase brake torque (same given pressure) you will get a gain, and if you 'over pad' the smaller rotor you'll likely over heat it. BUT, the size of the pad has no impact on the equation aside from the radial height of the pad. Meaning roughly where it sits on the rotor in aprox relation to the center line. The larger the pad, the longer the life of the pad, but it won't do a thing for torque. A pad with 6sq in vs. one with 12sq in of surface area has very little difference dispite it having more area.
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Regarding brake ducts, I've done Ghetto on our GTP for a track day, and I've done more "professional" on my Mustang, but I have pics of neither.
On the GTP I used 4-inch to 3-inch galvanized reducers from the Home Depot ducting department, hose-clamped to 3-inch semi-rigid aluminum ducting routed back to the engine subframe and then along the A-arm and pinched down to fit in the wheel and point up into the center of the rotor. The whole thing was zip-tied in place with the "scoops" exposed to airflow just under the outside edges of the front fascia...I would have used the foglight holes but the fascia and bracketry for the lights is not easily enough modified to be able to put it back when I was done. and held up fine for several weeks until I took it off since it's my wife's daily driver. Cost maybe $40 to do.
On the Mustang I fabricated some scoops out of long-taper funnels and screwed them to the bottom of the fascia. It's an LX so I don't have foglight holes to work with. I then used high-temp 2.5-inch silicone ducting (the expensive stuff) and ran it back and then along the A-arm to the rotor area. I was going to connect it to an exhaust reducer as a "nozzle" at the brake end but I couldn't get them in time for its inaugural track event so I didn't bother, I just kept an eye on the tubing to make sure it didn't overheat and it's been fine. Again, the whole thing is zip-tied in place with the exception of the brake end which is held to the spindle by a hose clamp pierced through the tubing and around the wire reinforcement of the hose. I'll get some decent pics of it all soon.
As for the technical discussion, BRAVO, I agree with Rara that it's for the good of the board. I am not a degreed engineer but I understand the principles. Farther up the board I was about to say that once the rotor reaches its saturation point it doesn't can't take any more heat and guess what, the friction coefficient changes and there go your brakes. But Rara beat me to it with a far more technical description than I can muster and then everybody started whipping out the greek letters LOL.
Then I stepped away, for a long time. Having a son and losing a brother in the same weekend kind of dampened my enthusiasm.
And I'm proud to be involved with a very intelligent group of "retards" who keep hashing this [censored] out for the benefit of people who may otherwise not have access to anything but "yo, dese are da shizzle-bomb, I saw them in a magazine".
Pacific Green '96 Contour LX V6
â??98 GTP, light mods, 14.66/94
Calypso Green '92 Mustang LX coupe, 13.56/101
Crown Autocross Club 1999 Street Tire Champion, 2000/2001/2002 Street Modified Champion
KCR SCCA 2002 Solo II Street Modified Champion
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