Reducing Understeer at the track
#1
09-22-2007, 09:11 PM
Join Date: Nov 2006
Location: Massachusetts
Posts: 109
Rep Power: 22 
Reducing Understeer at the track
I have been improving my skills at several DE events and I am starting to find a limitation with my 02 996TT at the limits. I am getting understeer plowing. I am running Bilstein PSS9's set at 1R & 2F, H&R Sway bars set to firm in rear, and med in front, and Michelin Pilot Cups inflated at 34F and 40R when hot as per the Michelin recomendations. The tires when warmed up seem very grippy and predictable, but I am still fighting the understeer. Any ideas as to what to try next?? 
#2
09-22-2007, 10:21 PM
Is the rear sway full stiff in the back? if not, do so. A good corner balance, maybe full soft on the front sway, front downforce will help, not sure how much the aero front lip spoiler provides. Also go to a more aggresive front camber, like 2.5 or more. I dont know the PSS9 settings but stiffer in rear and a tad softer in front helps me.
#4
09-23-2007, 05:29 AM
Join Date: Nov 2006
Location: Massachusetts
Posts: 109
Rep Power: 22
I will try a softer front roll bar setting. Kaizu, you mentioned less tire pressure. I did notice that with the MP cups that if they went a few pounds over the reccomended max they got slippery when hot. SHould I drop the tire pressure in the fronts or rears??
#5
09-23-2007, 06:13 AM
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Location: Finland, Luxembourg, Nürburgring
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Both if you want more grip 
Something like 2.2 bar front, 2.5 bar rear (is (32F / 36F, when HOT) gives you more grip with the Pilot Cups. Some might go even a bit lower.
The front roll bar setting might be crucial to your understeer, it should be on the softest setting. You might have an oversteering car after these adjustments so then start softening the rear roll bar.
Hope this helps.
Something like 2.2 bar front, 2.5 bar rear (is (32F / 36F, when HOT) gives you more grip with the Pilot Cups. Some might go even a bit lower.
The front roll bar setting might be crucial to your understeer, it should be on the softest setting. You might have an oversteering car after these adjustments so then start softening the rear roll bar.
Hope this helps.
#7
09-23-2007, 08:57 AM
I noticed when on throttle in sharp turns the rear weght bias does unduce a push feeling. Try to do the earlier suggestions and be meticulous with throttle modulation in the turns and then roll on through trackout. If your car is chipped powering out of turns or down straight is not your problem. You could also try to reduce wieght with seats etc. These cars are heavy. The front soft bar, tire pressure, and aggressive alignment should help. Good luck!
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#10
09-23-2007, 09:27 PM
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Join Date: Jun 2007
Location: Boulder, CO/Ft. Lauderdale
Posts: 108
Rep Power: 22 Both if you want more grip
Something like 2.2 bar front, 2.5 bar rear (is (32F / 36F, when HOT) gives you more grip with the Pilot Cups. Some might go even a bit lower.
The front roll bar setting might be crucial to your understeer, it should be on the softest setting. You might have an oversteering car after these adjustments so then start softening the rear roll bar.
Hope this helps.
Something like 2.2 bar front, 2.5 bar rear (is (32F / 36F, when HOT) gives you more grip with the Pilot Cups. Some might go even a bit lower.
The front roll bar setting might be crucial to your understeer, it should be on the softest setting. You might have an oversteering car after these adjustments so then start softening the rear roll bar.
Hope this helps.
Trail brake the snot out of it too.
#11
09-23-2007, 11:04 PM
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Join Date: Apr 2006
Location: Philadelphia, PA
Posts: 4,205
Rep Power: 204
If you really think you have maxed out the potential of your current setup (which is highly unlikely but plausable), then you need to invest in a REAL suspension from the likes of JRZ, MOTON or PENSKE. When I was at Pocono today, I had a similar problem and adjusted the rebound in the front down so it kicked back around track out and added more compression in the rear to slide it out a bit...it worked wonderfully. That said, understeer is very general term for the problem...WHERE are you understeering? Is it upon entry to the corner (turn in) or apex power application? Depending on where you feel it, you should adjust different things...as for MPSC temps...****...I run better times on higher temps with MY suspension setup...so I wont mention them...
You CAN have a neutral TT btw...
You CAN have a neutral TT btw...
#12
09-24-2007, 05:25 AM
Join Date: Nov 2006
Location: Massachusetts
Posts: 109
Rep Power: 22
Good tips, all! As far as to where am I seeing the indersteer. I am not having the problem on High speed turns. At Louden (New Hampshire International Speedway) in turn(s) 2 it is a slower speed fast - right then left, type 1 turn onto the short straight. The car engages PSM coming off the apex. Maybe I shoule be putting on more power?
#13
09-24-2007, 05:51 AM
Understeer Corrections
Push, plowing, front tires slide out first.
Usually slight understeer is safer.
Raise front tire pressure.
Lower rear tire pressure.
Soften front shocks. Stiffen Bump.
Stiffen rear shocks.
Lower front end.
Raise rear end.
Widen front track.
Install shorter front tires.
Install taller rear tires.
Install wider front tires.
Install narrower rear tires.
Soften front sway bar.
Stiffen rear sway bar.
More front toe out.
Reduce rear toe in slightly.
Increase front negative camber.
Increase positive caster.
Soften front springs.
Stiffen rear springs.
May need more front suspension travel.
Install wider front wheels.
Use softer front compound if possible.
Use harder rear compound if possible.
Remove weight from front of vehicle.
Add weight to rear of vehicle.
Drive a different line.
Use weight transfer to your advantage.
High Speed. Increase front wing downforce.
Too much front brake.
Vehicle is TWITCHY at limit and hard to keep
ahead of in the steering department.
Lower front and rear tire pressures slightly.
Suspension may be too stiff.
Shocks may be set too firm.
Tires may be old or hard.
Vehicle may not have enough suspension travel.
Vehicle may have a toe problem front or rear.
Increase negative camber front and rear if possible.
A properly set up vehicle will usually push slightly on corner entry, be fairly neutral at the apex (STEADY STATE) and exhibit slight power oversteer on corner exit. Tight courses may require more oversteer, fast tracks understeer.
Items needed: Accurate tire pyrometer, tire gauge, notebook and tape measure. Suspension information books.
Note: This is a sample of the methods used to correct various handling problems. Books have been written on this subject. Not every correction will always work as expected. Stiffer front sway bars will, in many cases, decrease understeer because of reduced body roll and better camber control. The best rule is to change only one thing at a time and keep notes.
Follow these suggestions at your own risk, RKR listed them to make your racing safer.
Last edited by cjv; 09-24-2007 at 05:58 AM.
#14
09-24-2007, 07:24 AM
Good tips, all! As far as to where am I seeing the indersteer. I am not having the problem on High speed turns. At Louden (New Hampshire International Speedway) in turn(s) 2 it is a slower speed fast - right then left, type 1 turn onto the short straight. The car engages PSM coming off the apex. Maybe I shoule be putting on more power?
Good luck great to see you on the track!
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