Another great video by Racers360, "Dealing with oversteer-what to do as a driver" I'm in
@HazardLvL4 Corvette C7.R GTE
at spa tomorrow and I'm dealing with this at the chicane 19/20 just before turn in.
Watched the video, and he is a very good source of information. Everything he stated is how I drive when dealing with a lively rear-end. Thus, he covered all the driving techniques, but I am going to cover the setup portion that affects corner entry oversteer.
*NOTE - The first change with the Corvette C7R GTE is to make sure the Longitudinal Weight Bias is all the way to the rear. This has nothing to do with your corner-entry oversteer issue, but this is a fundamental setup change for good overall balance in the Corvette C7R.
Rear Brake Lock-up on Corner Entry:
If the oversteer on corner-entry is occuring as you're braking, then this is typically due to the brake bias being too far to the rear causing lock-up or just unbalancing the car. In this situation you need to move brake bias a few percentage points back forward. Again the key give away for this is if it is happening under hard braking / lock up.
*Also if you are locking-up after you found the brake bias that feels the most stable, then begin reducing brake pressure till lock-up is eliminated or at least where you as a driver can mitigate it with your foot.
Too Soft of Rear Sway Bar:
If your rear sway bar is too soft then the rear will oversteer / feel unstable during corner-entry. You will need to stiffen the rear sway bar up one "click" at a time till you have stability in the rear during corner entry. The dead give away that you have gone to stiff is the car will then be oversteer happy on throttle on corner-exit. The thing to remember about the balance the rear sway bar provides in slow speed corners is:
Stiffening Rear Sway Bar = Corner Entry Understeer
Stiffening Rear Sway Bar = Corner Entry Oversteer
Softening Rear Sway Bar = Corner Entry Oversteer
Softening Rear Sway Bar = Corner Exit Understeer
*Remember the rear sway bar is working in coordination with your front sway bar. Thus, if your front sway bar is really stiff and the rear is really soft, then the front end of the car has a ton of grip and "pulling" the rear around the corners. If this relationship to too front biased then the rear will just snap or feel very unstable during corner entry.
Too Much Engine Braking:
Having too much engine braking can cause corner-entry oversteer as well. The reason is as the engine braking begins, usually about the time you have stopped braking to begin making the turn, the engine braking will be causing understeer, and you will be fighting that with you steering input to turn in. This imbalance can cause corner-entry oversteer. The simple fix for this scenario is to reduce the engine braking to a point where this no longer occurs.
Deceleration Ramp for Clutch Differential:
The Deceleration Ramp on the clutch differential can cause corner entry oversteer if it is too open. The fix for this is really simple just decrease the deceleration ramp one-click at a time till the rear-end is no longer oversteering or feels more stable to your liking. The relationship for Deceleration Ramp on Clutch Diff's is:
Increasing the Deceleration Ramp = Corner Entry Oversteer
Decreasing the Deceleration Ramp = Corner Entry Understeer
Tire Pressure Imbalance:
This is something that should always be on your mind. for the GT cars the tire pressures at all 4x corners should be 1.80 bar when the tires are up to temp. I usually have mine settle during a race around 1.84-1.87. If the rear tire pressure at hot temp. is higher than the front tire pressure you will begin to feel twitchy in the rear-end everywhere. This is why it is important in GT cars to keep all 4x corners at the same tire pressure at a delta of 0.01-0.02 bar.
Car Ride Height (Rake):
He covered this in his video and I don't need to re-hash it. However, one more key thing to remember when you begin adjusting the ride height to lower the rear to decrease rake, you will also be impacting the downforce efficiency of the car in the high speed corners. There needs to be a certain level of rake that way the rear is pressed by downforce to the point the car has 0 rake going down a long straight. This can easily be observed at Spa's main straight just after Eau Rouge / Raidillon. The car wants to be flat at maximum downforce to maximize the downforce generated by the floor. This applies to cars with diffusers like GT and Prototypes.
LASTLY, ONLY WORK ON ONE OF THESE AREAS AT A TIME. DO NOT TRY AND CHANGE MULTIPLE SETUP OPTIONS WHILE DIAGNOSING A PROBLEM!!!
I hope this is clear as mud, and if you are around before your race today I can share my Corvette setup or help you tune yours. Just let me know.
-Haz
