Quote:
Originally Posted by dcstep
18x10" 19-lb Apex ARC-8 wheels with 25 offset, 275-35/18 Dunlop Direzza Star Spec tires (square set up) 4.10 final drive, Dinan springs and camber plates with -1.8-degree camber up front and 1.5-degrees in back. Tire pressures, 27 cold in the back and 34 in front.
About tire pressures, AX is more about traction under acceleration and manhandling the car through corners by trail-braking the car on its nose. Low
TP in the back (combined with appropriately wide wheels) give better acceleration than high TP. Low pressure in back also helps the car to rotate in tight corners. You want enough TP in front so that you don't roll the tires, but that'll depend more on camber and wheel width, than temp and pressure. Usually, if you do find a big sweeper on an AX, it'll be midway through and your tires will have gained several pounds. I used to run the stock 19" Michelin setup with TPs very close to what I use with this wider setup and it worked great. 40-pounds will reduce acceleration and reduce tire effectiveness, IME.
Dave
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Quote:
Originally Posted by arter
I would set your tire pressures higher as autocross won't heat the tires ( and increase the pressure much).
With the soft sidewalls on PS2's I suggest 40-41....... especially if you don't have negative chamber yet.....
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Both sides of the spectrum and I'm right in the middle. Luckily with a 2 day AutoX I will have time to tune my setup. I think the real test will be chalking the tires and seeing how much is used. If 27 is too low and PS2 sidewalks are too soft then I can see how much sidewalk was used and add pressure. But what would be the indicator of too high tire pressures?
Normally I aim for 42 hot at Laguna Seca and have had success with that. With AX I go just a few higher than stock, hence 36/36. I will just have to test it tomorrow. But I do feel you on the lower pressures in the rear, maybe I'll do 36F/30R cold and see what the chalk says! Thanks guys!