In the Street classes (stock), you are allowed one inch change in wheel diameter up or down, no change allowed in WHEEL width, and +/- 7mm of offset change. Any tire you can stuff on a legal wheel is allowed. So if your stock rims are 16 x 6″ and you went to 17 x 6″, that would be fine. If you went from 16 x 6″ to 17 x 6.5″, even that small change is not allowed. The tire size does not matter, only the wheel. If you somehow managed to stuff a 315 wide tire on your legal 6 inch rim, we would all be amazed and congratulate you on finding the magic tire shop, but it would still be legal.
Matt Leicester
