8/10 with stock swaybars is the Vishnu/Gerrard spring rate ratio so that's probably not causing snap oversteer. Assuming the toe is correct (0 in front and bit of toe-in at back) then that is also fine. You ride height is close also. Therefore I'd assume something is abnormal. Perhaps the rear dampers are set too stiff? Has the car even been in an accident?

 

I don't think more rear camber is the answer--that will hurt you when powering out. Zero toe in the rear should work well w/ just a touch out in the front. Also, toe-out in the rear will make the car want to oversteer primarily when you're on the power--not off or dropping the throttle.

Your ride height w/ the higher front is giving the rear more grip--which is what you're looking for.

I think the higher rear spring rate bias is definitely causing the behavior--since you're not used to that. Tuning the dampers as mentioned before by softening the rear (which you've already done by running it softer in the rear) will help.

Ultimately you may need to get the rates equalized or reversed to suit your driving style. I know from experience I prefer a nuetral car, not one that's too twitchy. Now if I were into rallying......

 

It sounds like you may have a little toe out in the back, but it could be a few other things. Your rear camber is OKAY.

Also, you may want to try either lowering the front of the car or raising the rear. Just a smidge. I'd certainly check your toe settings first before messing with this.

Did you post your tire pressures? Glanced through and couldn't find them?


- Andrew

 

Tire pressures were initially (cool) 32f and 36r. this was not good.

Over the course of a couple sessions I lowered the rear down to 30 (along with softening up the rear dampers), and the car was more under control. I'd left the front at 32.

 

my wheel gap in the front is larger, but the distance from ground to jack point is actually an inch or so less in the front.

where is it apppropriate to measure the ride height?

 

If you were at 30 hot in the rear, that might be part of your problem. Too low IMO for street tires.

 

^ 30 cold (well, as cold as it gets in TX in June). I didn't get hot readings (instructor was giving feedback for 10-15 minutes at end of every session).

 

I hope Miles will correct me if I'm wrong, but I feel the best is to measure from the frame to the ground (level ground of course), so as long as the pinch seam has not been bent you can use the same point on both sides (front) and the same point on both sides (rear), also put your weight in the drivers seat when setting the ride height (use weights, sand bags, etc).

There will be variations when you measure to a body panel like a fender, should be more accurate and repeatable measuring to the frame instead. It should also make it easier to determine if you have the car raked.

 

FWIW I'm also reading 1" lower ground to front pinch seams than ground to rear pinch seams.

 

Thanks mad 8.

I think I'll leave my ride heigt as is, and work with the alignment, damping and tire pressures to get where I want.

I need to search for recommended alignment specs. some have already been proposed in this thread, mostly toe. I am leary about much toe because is kills tires so fast and I use my street tires for everything.

 

I hear that man, I'm running -2 F, -1.5 rear with minimal toe on the front (either 1/64 or 1/32 per side for a total of either 1/16 or 1/32 toe in up front don't have the sheet with me) and as close to zero toe on the rear as we could get it. Tire wear is not an issue with this setup and I do a lot of highway driving.

 

By looking at all your information, the rear spring rate would be the main reason why your car is oversteering. You are allowing more rear weight transfer than front. Of course alignment and driving style will affect too but if you have driven on the track with stock suspension and BC coilover and oversteer is quite significant then primarily it must be rear spring rate too high.

 

so, I don't mind oversteer. I mind un-warned snap oversteer into a spin.

since the spring rate ratio I have seems to be the most highly recommended by performance enthusiasts, I am trying to gather input on how to get the breakaway more controlled and gradual.

from reading all the posts, I think I have found an answer: adjust my toe settings, and then fine tune with damping and tire pressures. I'll report back ni October sometime how it turns out.

 

you know a small part of your problem may be your tires. I think the stock tires do not like modified suspensions at all. especially before they are hot or when they are hot*. pressure too of course.

last time I had any problem with the quick other way was on the stock tires.

 

I would definitely give Robispec a call and see when next he will be in your area and have him look over the car. Not only can it take you long to figure out the issue but it can be dangerous at the limit, plus he can advise you what will work.

Calling him is no obligation. PM me if you want his number.

Duncan