safetyfastgt

I'll give lower pressure a try. Hopefully will give me a bit more grip.

Norm Peterson

As darksky has said, you want to maintain the tires at whatever hot pressure(s) work best (it'll take a couple of events to zero in on what they should be, even with advice).

That's because when you're out on course - or even after driving on the street for a few minutes - your tire behavior is not going to know or particularly care what their pressure was when you first fired the car up in the morning.

I keep saying pressures in the plural because at autocross or any other activity where you're interested in cornering performance with little or no consideration for ride quality there is no reason to expect the front and rear tires (which get loaded differently) to need the same pressure. They might, but if so it'll be more by coincidence than anything. As a side note, I don't think I've ever run the same pressure all around even for purely street driving.

Pressures up in the 40's do apply in certain cases**, but I don't think that autocrossing a 3500 lb RWD car on tires of adequate size and wheels of adequate width is one of them. Think more like 35 - 37 front and about 4 psi less in the rear, measured right after pulling back into grid. If you want a stronger reference than just mine, I know that Sam Strano ran about 4 psi less in the rear on the Mustangs he was running as well (on R-compound tires).

Near as I can tell, owner's manuals and most other tire pressure references specify cold pressure because "cold" is easier to define than something vaguely between "warm" and "hot". It also provides a fairly consistent basis as ambient temperatures change with the seasons. They undoubtedly are set with the understanding that after the car has been driven a couple of miles or so that the pressures will have crept up a bit, and will then be at the design point for whatever ride quality and handling behavior was intended.


** Rear tires on FWD cars are often run at pressures up at least into the mid-40's range, as a means of getting cars that stubbornly understeer otherwise to rotate. I used to run about 37/47 in smallish RT-615 Azenis on the 626 when I was autocrossing it.


Norm

safetyfastgt

Thanks for the great explanation guys.

UPRSharad

I was told the Konis had 2 turns from soft to firm, but mine seemed like 2 to 2-1/4. That was before I drove the car though. I don't know if the adjustment **** will feel smoother or more free after having put a few street miles on the car, but I didn't want to twist on it too hard. I started out 1 turn above full soft on the front and rear (I assume this is what you're calling +1) and it felt fairly soft. I was considering increasing the dampening to +1.5 all the way around. But I'm taking note of your 1/2 turn stiffer in the front suggestion.

Fwiw, I'm at 35psi cold f & r on 255/45 and 285/40-18 Goodyear F1 Supercars. (OE GT500 tires) The steering feels balanced with the front bar on its softest setting.