03-24-2009, 10:31 AM
Darren raises more good points. Once you have a setting, use a good tire pyrometer and see how you're doing. You can find some guidance here: http://www.theracersgroup.com/news/show.php?id=372.
In short, tire temperatures across the face of the tire will tell you a lot about tire pressures, camber and toe. Here is the meat of that article:
Tire manufactures often list an ideal temperature range for their compounds. You’ll want to check with the tire manufacture to find out the ideal temperature range for your tires as a baseline. Race tires will be warmer and street tires cooler, for reference. Here is a simple chart to give some interpretation of the tire temperatures and what it means to your chassis setup.
Center of tire is hotter than edges----Tire pressure too high. Reduce 1 psi for each 5' F delta.
Edges of tire is hotter than center----Tire pressure too low. Add 1 psi for each 5' F delta.
Inner edge is hotter than outer edge----Too much negative camber.
Outer edge is hotter than inner edge----Not enough negative camber or too much toe-in.
Tire is below ideal temperature range----Tire pressure too high, tire too wide, or springs/sway bars too stiff at that axle.
Tire is above ideal temperature range----Tire pressure too low, tire too narrow, or springs/sway bars too soft at that axle.
Front tires are hotter than rear----Car is under steering (pushing). Too much front spring/sway bar, not enough rear spring/sway bar, front pressure too low, rear pressure too high, front tires too narrow, rear tires too wide.
Rear tires are hotter than front----Car is over steering (loose). Too much rear spring/sway bar, not enough front spring/sway bar, rear pressure too low, front pressure too high, rear tires too narrow, front tires too wide.
I usually have a memory pyrometer at the track.
In short, tire temperatures across the face of the tire will tell you a lot about tire pressures, camber and toe. Here is the meat of that article:
Tire manufactures often list an ideal temperature range for their compounds. You’ll want to check with the tire manufacture to find out the ideal temperature range for your tires as a baseline. Race tires will be warmer and street tires cooler, for reference. Here is a simple chart to give some interpretation of the tire temperatures and what it means to your chassis setup.
Center of tire is hotter than edges----Tire pressure too high. Reduce 1 psi for each 5' F delta.
Edges of tire is hotter than center----Tire pressure too low. Add 1 psi for each 5' F delta.
Inner edge is hotter than outer edge----Too much negative camber.
Outer edge is hotter than inner edge----Not enough negative camber or too much toe-in.
Tire is below ideal temperature range----Tire pressure too high, tire too wide, or springs/sway bars too stiff at that axle.
Tire is above ideal temperature range----Tire pressure too low, tire too narrow, or springs/sway bars too soft at that axle.
Front tires are hotter than rear----Car is under steering (pushing). Too much front spring/sway bar, not enough rear spring/sway bar, front pressure too low, rear pressure too high, front tires too narrow, rear tires too wide.
Rear tires are hotter than front----Car is over steering (loose). Too much rear spring/sway bar, not enough front spring/sway bar, rear pressure too low, front pressure too high, rear tires too narrow, front tires too wide.
I usually have a memory pyrometer at the track.
Chris
981 GT4
996 GT3 Cup
911 Carrera Sport Coupe
PCA Nationally Trained DE Instructor #200810247
Genesee Valley BMW CCA Instructor
981 GT4
996 GT3 Cup
911 Carrera Sport Coupe
PCA Nationally Trained DE Instructor #200810247
Genesee Valley BMW CCA Instructor