Originally Posted by TrackRat
Over 40 psi has no particular significance.
Actually it does - you need to be aware of what the max psi rating is for your tire. I would not recommend starting your pressure at 40 psi for the OEM PS2's for example which is max 50 psi - I usually started mine around 31-33 and after a session they generally get to around 40 and seemed to perform fine although the get a little greasy after 4 or 5 laps. I have seen tire temps start at 31-33 and go as high as 45psi which in my opinion is too high for this tire and this car which leads to premature wear and lots of oversteer (although that can be lots of fun