For AX, is the widest, lowest profile tire that will fit generally the best performance option? Is an 18" wheel generally better (higher performance potential) than a 17" wheel? I have points to give so that isn't a big factor and information on what will fit (what options I have) is out there but it seems to be an underlying assumption to go as wide and low as you can. Is that the answer? I'm trying to decide if I should buy different wheels as well as tires.
My 968 has 17" cup wheels with well toasted 225/45 fronts and 255/40 rears. They also came with 16" wheels, and it appears that the 18" turbo twists with 225/40 fronts and 265/35 rears off my 2002 Boxster S will fit as well (but a swap won't work as the 17s hit the calipers on the Boxster I think). Would the 18" wheels and tires be a performance upgrade for the 968? Should I just get wider tires for the 17" wheels? Any thoughts on approach, other options to consider would be appreciated.