avizandum

This is in AutoX situations mostly in corner exit situations:

I manage / utilize oversteer in corner exits, but I have spun out with no warning half a dozen times this year. I'm running 0.8 neg camber and 1/8 total toe in and while this is basically the setup I ran last year, a different shop did the alignment.

I don't believe those machines with the laser reflectors are all that consistent from machine to machine...

I've heard of guys running up to 1/2 total toe in, but this is my DD, so I can't go that extreme. Any words of wisdom?

davidfarmer

I've never heard of running more than 1/4", or .8deg total. However, since autocross mileage is low, it won't hurt anything as long as you stay off of the street.

You burn up your tires running that much toe on the street, even 1/4" causes excessive wear.

naschmitz

I experienced the same last year. Mid corner it would just pull the rug out from underneath you with no warning. I had an instructor drive it too and the same happened to him

I was running the C6Z51 bars front and rear. I have since changed back to the C6 Base rear bar (along with a million other changes since then). I did notice that the bushings were grabbing on the C6Z51 bar so tightly that they sheared the paint off. I hadn't lubed them or put in washers to keep the mounts from compressing the bushing. So binding the rear bar might have been the cause.

Sunday I have an autocross where I am going to put the bigger bar back on with lubed poly bushings to see if it was a binding issue or not.

I've been doing my own alignments and I haven't seen toe affect snap oversteer, unless your rears are toed out. That you can measure yourself. I mention this because if your alignment shop did not tighten the alignment cam bolts tight enough, your alignment will change if those cams rotate.

Hope you find the cause. Kind of takes the fun out of autocrossing when you have an unpredictable setup.

avizandum

I'll take a look at the bushings. Post how things go tomorrow...

Slalom4me

Your oversteer is occuring under power on exit, not under braking
on entry, correct?

.

avizandum

Correct.

napacruzerc5

Throttle oversteer? At a recent autox I tried staying in 1st instead of short shifting to 2nd...and around I went at the exit to the first corner. Even on some of the shorter courses I usually short shift to 2nd since
1st will just break the rear loose. My $.02

Davinss

Have you done anything to the car since the last alignment? Ride height? Shock change?

Post your whole alignment and exactly when it was last done.

TMyers

Are you still running runflats? If so that is you biggest problem.

My Alignment is as follows:

Front
Camber -1
Toe Total .04"

Rear
Camber -.5
Toe Total .02"

Air pressure before a run, 36psi front, 32psi rear.

I am running Kuhmo XS tires. I only have three races under my belt, 2 last year and one this year. This is my first full year of autocross. My car is a F55 stock otherwise and a DD.

Last year with runflats, not supercar, the car was snappy under acceleration and pushed like crazy under braking. Adjusting air pressure did not make any difference.

This year the car is very neutral provided the tires are warm. The car does not push under braking. Once the car is set I can pick up the throttle and accelerate thru the corner. I can still induce oversteer by applying to much throttle but it is not snappy like last year.

I understand that I am just a novice and still have alot to learn. But so far this is much better than what I experienced last year.

naschmitz

Only got four runs in today due to a thunderstorm, but I definitely did not have any snap oversteer going back to the bigger rear sway. Again, this time I mounted the sway in a lubed poly bushing instead of the factory rubber one which might have been binding and tore all the paint off the bar.

Obviously this made the car looser, but it was predictable in the 180-deg sweeper.

So I'd check your bushings and also measure your rear toe just to be sure the alignment cams haven't moved since your alignment.

Bert

svcjmo

You are more than likely bottoming out on the shocks with spring rate going to infinity...especially if a bigger rear bar helped.

Jerry VetteSport

Solofast

Yup, that's what it sounds like to me too. The bigger rear bar was restricting the roll and keeping you off the bump stops, but with the smaller bar you were bottoming...

naschmitz

I don't know if it was the original posters issue, but the smaller bar was not my problem. I was getting the snap oversteer from the bigger bar and fixed it by going to the smaller bar. My guess is that the larger bar was binding up in the un-lubed tightly clamped rubber bushing and releasing mid-corner. With a lubed poly bushing the larger bar works fine.

Solo2GS

I can't imagine the C6 being to different from the C5, but the C5 likes stiff in the front and soft in the rear. Big rear bars are not favored in AX. Most set their adjustable bars and shocks to soft in the rear. Obviously if you are stock there is not much to adjust in this aspect.

As someone else already mentioned, short shift into 2nd and stay there. On a typical AX you should not have to down shift. If you do you are lossing time. We have enough grunt to take even sharp corners in 2nd. Only very rarely do I ever down shift and usually only on a tight 180 turn around.

Tire pressures can also adjust the handling. To high in the rear and it will be have more oversteer tendencies. Try lowering the rear pressures.

Many in AX run zero toe in the front. I run zero toe in the front and 5/16" total IN in the rear. My car is not driven on the street. Rake will aslo help with turn in. Have the rear .25-.5" higher than the front.