Are you all that are runnin the 315's using a 10" rim? My budget for next year includes the money for some real 18" Saleen wheels. I want to run 315's in the back and 265's up front with some Nitto 555 rubber. So 265/35/18 and 315/35/18. How about wheel spacers, is it just for the look or are they necessary? I'm running 2.5" tails with no suspension upgrades. The last thing, this rolling fender part I keep hearing about, would my particular case require it? Any answers would help guys, thanks.
275's will fit a 8in rim, remember though that the tire will have a bulge fro a sidewall. Also some brands (NITTO) run smaller. A friend had 275 nitto DR on his stock 00gt 17in rims and they fit fine.
You will prob get better performance out of a correct tire size for the rim width vs. trying to stuff wider rubber on a smaller rim.
315's should be mounted on at least a 10.5 wide rim if we are talking about 17in rims.