Just became 3rd owner of 97 C2S which is on nonstd Speedline wheels which I blv was OEM for the 993RS. Front 8J rims wearing Potenza SO2 225/40ZR18 Rear 10J with same SO2 265/35ZR18. Unfortunately came without the handbook. Can anyone help with info on correct pressures? Thanks.

 

There is no correct tire pressures. You must experiment and find the right set of pressures for your driving style. Try 34F and 36R and see what happens.

 

I had to reduce my front tires pressure down to 30 to reduce the sensitivity on the steering. I have OEM 17". I am still working to find out what the back should be to get a balance with the low front pressuse.
HN

 

Go to my-porsche.com to buy an owner's manual - which contains a wealth of essential info.

Can't help w/18" pressures. FWIW, I run 34F/36R (cold) on my 17" Michelins.