Re: Tyre Pressure You are certainly on the right track, however I'm sceptical about the part "because your traveling longer distances and at a higher speed for longer so the expanded air cools down" http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=72
Aftermarket wheels & tyres Re: Tyre pressures go out the window with aftermarket wheels. Manufacturers that fit 17", 18" & 19" wheels to their vehicles recommend cold tyre inflation pressures similar to the Z32 TT (Front 33 & Rear 36). As an example: http://porsche.michelin.fi/wp-content/uploads/2011/10/Porsche-Michelin-Fitment-guide-2006-12.pdf
