Contour Enthusiasts Group Archives Forums Modifications Brakes Okay I'm a newb so school me

in this thread:
Link

there is talk of knockback. What is knockback? would it be similar to a pulsing brake feel? And when would you feel it? (under normal braking, heavy braking?) I would like some info on this. I've been having a pusling brakes downhill and if something is going wrong with the bearings/knuckles I would want to know ahead of time...

I've been told that brake pulsing downhill could also be due to thin pads. Thin pads heat up faster and then the brakes are going to crap. I don't know if that is true either. I haven't had time take off the tires and check either. So heres your chance to school me, cause I need it!

Edit:
Figured I'd add in that the pulse doesn't occur in normal braking on level ground. So I doubt its the rotors.

Knock back is a phenomenon where the rotor flexes or moves in relation to the cliper and thus pushes the pads (and cylider) away and then when you go to press on the brake you get a mushy feeling and then it gets frimer after a few more successive pushes. It's nothing to do with pulsing from warped rotors which it sounds like you have.

what stazi said, except what people perceive as "warped rotors" are very very rarely actually warped; 99% of the time (or more) it is actually uneven wear of the rotor resulting in variations of the rotor thickness. This thickness variation is also commonly called Disc thickness variation, or DTV for short. Many things can cause it, but, the most common cause is lateral runout, either of the rotor itself, or the hub and bearing. LRO allows small sections of the rotor to just touch the pad every time it goes by during normal driving, and eventually wears a thin spot in the rotor.

I think you have a case of DTV that is just starting to get noticable. You can replace the rotors, or have them turned if there is enough material left.

rotors are alot nicer then bearings The question is now do I want to buy the brakes and get the bigger rotors and new pads. or just buy a good replacement set. I'll just keep using this thread and ask:

How much of a braking gain( or loss in distance depending on perspective) is there from the 260 rotors to the 278. It seems to me that another 18 would cause a decent amount of improvement and there really no problem in having better brakes.

Oh and thanks for the info above. Still learning all this stuff. I've never heard of DTV before. Does anyone ever think that you should have to learn/know some of the stuff like this to actaully get your license?