Contour Enthusiasts Group Archives Forums General Autocross and Open Track Adjustable Anti-Roll Bars - One or Both End?

Here's something to think (and debate) about...

Premise: You only need to adjust one side of an adjustable anti-roll bar and in doing so you will NOT introduce asymetry into the load transfer/roll rates.

Why?

An anti-roll bar is a linear rate torsion spring. Only the center part of the anti-roll bar transfers the load and it could care less about the lengths of each end. The center part of the anti-roll bar sees both bar ends as one lever (which is the combined lengths of the two bar ends). Each end is totally dependent on the other because you can't disconnect one end and have the bar still work on the other.

Let the discussion begin...



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John Coffey
johnc@betamotorsports.com

[This message has been edited by johnc (edited November 06, 2000).]

[This message has been edited by johnc (edited November 07, 2000).]

Sport Compact Car did a little editorial on sway bars a couple months ago. Let me find that and my Carroll Smith books before I say anything! No, I can't wait...

Seems that you would end up with an aysymetrical effect, as one side would produce more or less leverage on the center of the bar.



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Chris
2000 SVT

Chris,

Why do you think yopu would get an asymetrical affect? And what would affect be?

GRM did an issue on anti-roll bars and they didn't discuss this.

Save your time on the Carroll Smith books. He doesn't talk about it directly. He does mention that when he sets up cockpit adjustable anti-roll bars he makes both ends adjustable.

BTW... I spent two hours on the phone with Carroll talking about this exact issue. And I'm not going to tell you what he thinks... yet.

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John Coffey
johnc@betamotorsports.com

[This message has been edited by johnc (edited November 07, 2000).]

[This message has been edited by johnc (edited November 07, 2000).]

If you've spoken with the man and you're arguing the other side, I must be wrong!:O It won't be the last time!

Seriously, about all I can remember from the article in SCC that I read (and can't find) was that the length of the bar was the pertinent factor. By adjusting the bar in an asymetrical manner, it would seem to me that your moving the imaginery fulcrum. You'd be givng more leverage to one side or the other.

When I think of this I'm not imagining a sway bar and end links. I'm seeing a straight axle sprint car with torsion bars. If you move the axle further away from the torsion bar mount and use the same arm, it will have more leverage on the mount with the longer torsion arm. If it were possible to cant the axle at an angle to the mounts, the same arm would produce different spring rates at opposite sides. ????

I also see this. If I go out, disconnect the drivers side sway bar and try to pick the passenger side wheel up with the driverside bar by itself, I won't be able to budge it. If I attach a long enough lever to it, I will be able to. With the end of that lever now attached to the drivers side control arm, I will not be able to pick up the drivers side wheel with the passenger side end of the sway bar.

My head hurts! God, I had to decide who to vote for today, and now this...... UGHH!



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Chris
2000 SVT

My head hurt too. I had to think about this and make little paper cutouts.

FYI... Not all suspension designers or race car drivers agree with the original premise above. But if you look at the super trick blade anti-roll bars you'll see that many of them are adjustable only on one side.

What gets confusing about this discussion is that we are talking about one thing (lever arm length and the distance the lever arm travels) and then trying extrapolate that into independent forces acting on each side of the spring. You cannot look at each side of an anti-roll bar as acting independently. Its all ONE linear rate spring.

BTW... Carroll Smith generally agreed with this although he thought that in extreme long suspension travel situations where both wheels were traveling in the same direction (i.e. a car going over a speed bump) you would see some asymetry. But this would be irrelevant in a racing situation.



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John Coffey
johnc@betamotorsports.com

What brought this up anyway?

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Chris
2000 SVT

I kinda post these discussion topics to the various lists/boards I subscribe to (Team.Net, 240Z.org, CEG, Solo2.com, etc.) as a change from the usual topics. It gets people to really think about the underlying theory behind the modifications they make to their cars. Plus, the responses get me thinking about what I think I know.

And I get tired of 600 threads about the best oil to put in your car...

BTW... If you ever want to talk with Carroll Smith about racing, suspensions, etc. just send him a letter c/o Earl's Performance 189 West Victoria Street, Long Beach, CA. 90805. Describe your question/issue and if he finds it interesting he'll give you a call or ask you to call him at home.

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John Coffey
johnc@betamotorsports.com

[This message has been edited by johnc (edited November 08, 2000).]

Hey John !!!

It is great that you are making the effort
to "raise the bar" on our dialog!!
To be honest with you I am about as green at this as they come. I have completed my first
season of SCCA Solo II and have enjoyed the
running and the people! As lame as this sounds , I can now feel what a 5lb pound difference in tire pressure does to the car!
I did not want to make a mistake by throwing
"parts" at the car my first season. I heard
before that SOLO II is 80% driver 20% car.
So I just worked on my driving and got a feel for the car now I am ready to work on
the areas I need help on. Which are Suspension and line choice on the track!

I have been a race fan for ever and when I was a child my dad raced dirt-track in southwest Texas ,New Mexico and Southern Calfornia. I have never been "stable" till now to have the money or time to try my hand at this! But I finally got involved last April and have been hooked ever since. My second race was the SCCA National Tour at the Texas Motor Speedway and talking about being lead to slaughter! But I learned more in those two days than I learned all season! Talking to the other guys and watching them run.

Most of the reading and our local drivers run rear wheel drive cars. I assume that having front wheel drive our setup is the 180
from a rear drive car? I hear that the course lines are the same between the two types of cars . There is not alot of info on setting up my car. I have found a few web sites "team SCR" and "club DSM" which have helped alot.

So any Basic 101 setup would help and as we grow I feel that the dialog will go away from
"how often to change my oil" to weight balance and car control!

Please keep raising the bar some of us may not have alot to say but I just wanted to let you know we are reading and are grateful
to you for your time and knowledge!

Vern Kilburn
Contour SE
Dallas,TX

What a way to get started in the sport... at a National Tour! If you got through that and had fun then you're set.

Setup for FWD car is somewhat different from a RWD car, but its not that different. Again, your focus on yourself is the right thing to do. I've been autocorssing seriously since 1996 and I still prefer to spend money on driving schools as opposed to my car.

BTW... its off topic, but here's my pride and joy - http://www.240z.org/rides/jc.htm


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John Coffey
johnc@betamotorsports.com

[This message has been edited by johnc (edited November 09, 2000).]

Yes I'll be doing phase one and two at Evolution Driving school in Febuary
before my season starts WITH the changes that I am making to the car. The changes are converting a Contour SE up to the specs of the SVT. I will use the 19mm front swaybar from the SVT and a 22mm rear sway bar from
BAT. Koni Yelows front and rear and H&R Sport Spring Set. From my reading they are a little stiffer than Eibach springs. Move to 17" wheels and 215/45WR17 Yokohama A520 for tires,better brakepads.

Hey the "daily Babe" on you web site is NICE touch!

Again any two cents is welcome!

Vern