Autocross tire pressure for stock tires?

[joe149]

I'm headed out to my first autox tomorrow. I'll be driving up on the OEM tires and will use them (probably use them up!) in the autocross. Any suggestions about what pressure to set them to? Should I set them cold before I leave? They will gain probably 4 lbs just driving up there. What should I be aiming at as a hot temp front/rear?
thanks,
Joe

 

[Shadow102]

Car and tires would be helpful

 

[joe149]

Funny - that just occurred to me. Doh!

Mazdaspeed3, Bridgestone Potenza RE050A, worn to the wear bar indicators, so I figure this is the end for them!
thanks,
Joe

 

[Shadow102]

Start with 40psi front and 36ish rear and go from there

 

[joe149]

Thanks Shadow - that sounds about right to me too.
best,
Joe

 

[Auto-Xer]

I'd start about +5/+4 to that. I ran 225/45-17 Kumho SPTs on my otherwsie stock Mazda6i last week and settled on 45/39. That setup worked very well.

Unless these Bridgestones have really stiff sidewalls, I think 40 will be a bit underinflated...especially on a car like the MS3 which can punish front tiires.

 

[joe149]

I wouldn't argue that more pressure might have been better, but at 41/37, the car did well - no excessive plowing, etc. Oddly, when I had the traction control and the stability control ON, it DID understeer pretty badly. I turned them off for remaining runs, and the car was excellent. Only one part of the package I think needs improvement is the driver...
thanks for advice,
Joe

 

[Cellerator]

For stock 16 in rims with the toyo 4 seasons, today I used 37 front and 34 rear, next time I think I'll add another 2 psi because I was still wearing a tad too much on the outer edge but it felt very good. My car understeered quite a bit but wasn't unbearable since I expected it from a fwd car. This was on an asphalt parking lot that has lots of gravel. I was faster than a 911 in the afternoon session pax wise and 2nd place overall in the morning session, 1st in street tire.

This was the layout for this morning:

The afternoon is reversed with 2 boxes before the finish and was not as fast.

 

[joe149]

Just FYI - did the autocross with 40/36 after driving to event. They gained 1 lb after a run, to 41/37. No edge rollover, no excessive understeer. I'd recommend these pressures for pretty much any street tire.
Joe