Car scooots right under heavy brakes.

[cygnusx1]

Race tracks don't have much crown, if any. Would it be safe to say that correcting the wheel wheelbase differential for a race car would be OK?

 

I'll guess an answer at that by saying, race car suspension setup would be so far off of a mild street setup, that the wheelbase difference would be shadowed by other angle changes anyhow. Correct?

 

I don't want to jump to conclusions yet, because if I just blame it on road crown or wheelbase differential, I could miss a more serious problem.

 

This has turned into quite an interesting thread.

 

 

http://beluap.tripod.com/crash5.html

 

"Unequal caster causes the vehicle to pull to the side with the least positive caster. Unequal Caster Effect - to offset road crown, the top left steering knuckle is always leading the right; the right side has more positive caster."

 

My car does NOT pull during cruise, only under medium to hard braking. But it does not pull hard. It kind of settles into a slight rightward tendency...if you can imagine. This caster differential/wheel base differential could be it.

[johnc]

I don't have an aswer as to why the 240Z has a slightly longer wheelbase on the right side of the car and its not something I try correct on a race car. Its never really been an issue I've spent time studying. There are many other, more important issue with the strut based suspension on the 240Z that, IMHO, a slight wheelbase difference is low on the priority list.

 

If I ever get time to setup the S30 in the Mitchell suspension geometry software I have I shoudl be able to figure things out.

 

Also, since the original problem only appears under braking, I would go back and look at the TC rod, the brake system, etc. I would also rotate the tire left to right.

[JMortensen]

Race tracks don't have much crown, if any. Would it be safe to say that correcting the wheel wheelbase differential for a race car would be OK?

Yes, which is why I said the caster measurement is more important than the wheelbase. This may sound stupid, but if this happens when you hit the brakes, hitting the brakes has something to do with why it happens. Caster being off will cause a pull all the time. A bushing compressing under load and changing caster will cause a pull under braking. Based on what you said about your TC rod bushings, I'd be checking and making sure everything is tight and then moving on. The next most likely culprit is going to be the pistons in the calipers on the right side I think. I doubt the rear toe setting would change in a consistent way to cause a pull to the right every time. I could be wrong, but I think you're barking up the wrong tree there.

[tube80z]

I see that you have AZ racing brakes, which I believe are wilwood superlites up front. You need to clean the pistons on these periodically or the brake dust can cause them to hang up. Also check the pads for taper wear. One trick we use to get longer pad life is to flip the pads up/down/in/out after a few events.

 

You have a number of options if you don't find a caster issue. Swap tires, then swap pads side to side. Those are all easy. My guess is one of these would solve the issue before you need to look into anything more sinister.

 

Cary

[cygnusx1]

Here is my plane base on what you guys said:

 

1) Take the rotors to get surfaced. They are slightly bumpy.

2) Check the cleanliness of the pistons.

3) Measure the wear of the pads for even-ness.

4) Take the washer out of the left TC rod bushing.

5) Do a routine fluid change.

6) Take some measurments of toe and caster again.

7) Ignore difference in wheelbase.

[Spooler]

Did you ever get this issue fixed? I have had this issue before and it was due to worn rack bushings.