40 psi is what I'm running. sometimes a bit less. The surface that your on has a major influence on this. The surface I deal with is pretty rough for asphault. Probably why I only need 40 psi. If I put in anymore its like being on ice. The car actually likes less air pressure but (better grip) the tires roll onto the sidewall then.
I've cut down to 35 psi in the rear tires and it was my best overall performance yet last time I was out.
You should almost always use as little as possible at first to keep the tires from rolling under. Learn how to control the car, then start playing with tire pressure. I know I'm still learning how to drive a FWD in autoX. Tough lesson coming from my old RWD big V-8 car. I also seem to go quicker when my tail end never comes out. The times is does, I end up going slower. T
