I am considering buying some Pirelli Slick ( scrubs ) rather than my typical Hoosier R6's. The Pirelli's have a sizing I'm not familiar with so though I would check with the 6Speed board. I normally use 235X35X19" and 295X30X19" and the Pirelli's are sized the following: 235X645X19" and 295X680X19". Anybody have the know if these will work?

 

slick sizing has the 645 and 680 numbers corresponding to the tire diameter in centimeters. So 235x645.19 = 25.4" and 295/680/19 = 26.7". The stock tire diameters on the 997 are 25.6" front and 26.2" rear. The ratio of the slick diameters is 95% F:R and stock is 97.7% F:R. You are within 3% and I am speculating that is probably ok. The trouble is whether the wheel speed sensors and differential will trigger the PSM with a non-standard ratio.

 

The Pirelli tire sizes 235X35X19" and 295X30X19" used to be for the 360 Ferrari Challenge. Not great at all if you have 12'' rim at the back.