danswofford

I'm experiencing oversteer at turn entry.
02Z, -2 camber Front, -1.5 camber rear, no toe front, 1/4" toe in rear. Kumho 710, T1 sway, coil overs, 700#F/600#R, poly bushings. Front splitter, no rear spoiler.

I'm not trail braking. The car sticks like super glue from the apex out.

As soon as I turn in the rear wants to go sight seeing.

UstaB-GS549

Sounds like toe out in rear. Under braking?

emf

Sounds like it could be balance as well . . . splitter, no wing or spoiler may be upsetting the balance of the car at speed . . . I've created similar on a non-aero car by jacking too much weight forward. Sticks great on the exit, since weight transfer shifts back under power.

larryfs

Too much rear camber.

Don Keefhardt

What's your throttle foot doing from entry to apex ? Not trying to be a wisea$$...a serious question...really.

Did this problem suddenly appear, or has it been this way for a while ?

When's the last time you had the shocks out of the car for a 'look-see' ?

Whacked any curbs lately ?

Play around with ride heights lately ?

danswofford

I brake hard while straight, then off the brake and back on the throttle somewhat to the apex then add gas as I can at and after the apex.

Been this way.

New shocks. LG's coilover with Bilsteins.

No curbs,

Lots of screwing with ride heights but I have not been able to get it corner weighted yet. Could be way off.

danswofford

You might have it there. I've been trying to find a decent wing and also thinking about fabracating up one out of carbon fiber over foam. I'm trying to find an airfoil shape.

Olitho

Go out driving with me and EMF. We can swap cars and see how the three cars handle. I have noticed my car will over-steer as you describe with my Hoosiers down on even a couple psi.

I will be out at Streets of Willow this Wednesday as is EMF I believe.

emf

The obvious trick is to use a low-speed, high-lift airfoil . . . . problem is, most high-lift airfoils will need a matchingly massive splitter. I've got the actual airfoil info for mine scribbled down somewhere at home, but am at the point where the addition of dive-planes sounds like a good idea.



As a test, jack more weight to the rear of the car -- You'll probably end up creating problems at low speed, but it should confirm where things are going seriously wrong.

RE alignment, toe seems a bit agressive, but camber should be OK. Normally, I'll run 1/16th in at -2.5* on slicks and R's.

C5inWV

One of my favorite magazines, Grassroots Motorsports (May '06) made some suggestions regarding balance/ tuning.
The article was specifically about shocks, but some of the solutions offered for entry oversteer were to stiffen the front springs or the front shock compression. Don't raise your front ride height for this problem. The front ride height is generally as low as possible. You may want to recheck the rake; have the rear 3/4" to 1" higher.
If the car is set up right, you may try changing your driving style. Easier said than done, right?

rikhek

I agree. Try -1.0.....

Rick

danswofford

Next time out I'm going to add a little bit more front spring, a little bit more rear tire pressure and a real smooth turn in.

XPC5R

Sounds good, but don't add any rear air - it will get looser - not sure what the track guys run for air, but you want the rear's 3-5psi lower than the front - the kumho's will tolerate very low air on a car with good suspension control (as you have) - I have been as low as 20psi in the rear with 315/18's to try to get traction.

Lower the rear of the car a bit if possible (reduce the rake), that will help reduce corner entry oversteer.

FasterIsBetter

My first thought when reading your comments (and the easiest thing to play with) is tire pressure. If you've been going up with rear pressure to try to get more rear traction, you are going the wrong way. To start with, the rears should be slightly lower psi than the fronts, and if the oversteer is there, bring the rears down a bit more. In my experience with the Kuhmos, they like to be a little on the soft side to start with anyway. Check your tire temps immediately after a run to be sure you are not too far over with the camber and your pressures to be sure that they are not changing relative to each other when they heat up.

Vetracr

Its possible you don't have enough rebound control on the rear shocks. Under heavy braking the nose is diving and the rear lifting. You are unloading the rear tires as they lose camber from droop combined with a loss of toe in. Not a good combination for good corner point in on a Corvette. My $.02.

Larry

Don Keefhardt

This just screams 'suspension setup or alignment' to me.

Get it on some scales. You could be all whacked on crossweight, but with stiffer suspension it won't be visibly apparent.

Check the rake. If you've got a roll center too far out of kilter with the other end of the car, you're gonna have issues on corner entry. Also check your rear toe numbers, and maybe check bump-steer.

Have a trusted somebody ride in the right seat, and watch your feet on corner entry. I refer to it as the 'unconscious trail-braker'. IME, a majority of people will SWEAR that they're off the brakes and onto the throttle when the steering wheel starts to turn...but reality (and somebody sitting in the passenger seat watching feet and hands) says different. You can sit there and WATCH start cranking the wheel while still on the brakes, and they'll still swear that they're not doing it. My motto: "Know thyself".