James
When you say the D90' SE wheels, do you mean the CS wheels with the traced groove ?
If it is these I would recommend you avoid doing trackday on them - I have witnessed first hand refurbed CS wheels cracking across the spokes when they're very thin. I recently saw and have a paper copy printed out at home of a comparison of 16" wheels - despite the CS reference, compared to original D90's there's ~ 1kg difference per wheel.
Anyhow, back to the original question... I think you have to experiment with tyre pressures for your car and driving style, subject to the track and the temperature.
I'd start with say 32psi at the front and 34 psi at the back from cold and then measure them again after ~ 5-6 laps. Undoubtedly you'll find the pressure will go up and then you have to drop them down again. Unless some of the chaps with greater experience or racing knowledge say different (happy to be corrected....) I don't believe you go above 38psi for any tyres as you risk 'doming' the tyre, wearing out the middle and reducing grip.
The original Porsche factory settings for 944's and the 951 have the tyre pressures very high. Two points to consider:
1. Since the last 951 left the factory in 1991 (or 2 ?) tyre technology and in particular side wall stiffness has changed dramatically
2. 944's were designed partly for use in Germany on derestricted Autobahn's at > 100mph - from a liability perpsective you always have to have the tyre pressures higher to ensure that heat build up at speed (frequently caused by under inflation) is limited.
Last but not least, enjoy your track day !
