I'm switching over from 16" to 17" wheels and from Toyo T1R's to the Dunlop Star Specs. The Toyos are great street tires but sidewalls to soft for autocross and I need to inflate to about 41 or 42 psi to prevent rollover.

What cold or hot air pressure are people using in the Star Specs at autocross?
I know I'll need to experiment, but I want to hear what others are using so I'll know what not to do. Thanks

 

What suspension and what size wheels? I can give decent advice for stock suspension (stiff front swaybar) and stock size wheels.

 

I've got the stock CR suspension on my AP1 (springs/dampers/sways) and will be running 17" wheels with Star Specs 225f/255r.

The CR suspension is much stiffer than my stock '03 AP1 with spring rates at 375f/264r as opposed to 240f/230r. Sway bar is bigger up front (28.6x+4.5 vs 26.5x+4.5)

 

I run 34 to 36 psi on Star Specs mounted on stock AP1 wheels.

 

I have run 36 front / 32 rear on the 225/255 17" setup with stock wheels, on my AP2 non-CR with 1.25" solid front swaybar. That should get you pretty close.

I'd like to know how you determined what those spring rates were. I have been trying to track down a reliable source for what any of the spring rates from 2002-2010 were. I have all the relative change data but not the absolute rates.

 

They grease up when the pressures rise into the 40s

 

[QUOTE=Orthonormal,Aug 17 2010, 04:18 PM]I have run 36 front / 32 rear on the 225/255 17" setup with stock wheels, on my AP2 non-CR with 1.25" solid front swaybar.

 

Thanks. I won't start them at 40 but will try 36f and 32r.

 

35 all the way around feels good to me. If your car pushes or oversteers this will change. I think optimum grip is around 35.