I've been debating a 17" or 18" wheel set. I settled on the 17's due to tire sizes. I don't want tires so thin they won't protect the rims or help with driveability.
I will say though, that the rear wheel opening has enough room to run an 18" rim without getting too short on the sidewall. The front, on the other hand really is limited to a 17" rim, IMO.
If money were no object, I would run a 245/45-17 on the front and a 275/40-18 in the rear. Both have about 4.3" of sidewall, and they match a C5 Vette for tire size. Makes them a size that should be readily available for a long time, and relatively cheap to boot.
