worrying about rim size should only matter if you go to the track and race the car. I have my 17" gsx rims with a 50series tire, but if i go to the track i just swap them and put my 14s on. I plan on getting 18's when i get the cash. Who gives a damn if you're a tenth of a second slower on the streets, put on the 18s (public streets are not for racing), but if you take it to the track, then just swap in the 14's. The only problem is that 14's will cause lots more wheel spin than 18s will.