Rim help

[Kissner]

I'm looking to replace rims and i'm wondering what size i'm gonna start running into problems with. I drive a 98 M3 and am looking to put the same size rims all the way around for rotation reasons. I know that i can fit a stock 17x8.5 in the front. I need to know the stock offset and stuff so i can be sure to buy the right size so there is no rub issues. Can somone please let me know the stock offset? Also, i'm looking to go from 17's to 18's. When i move up an inch in rim size, does that inch just get taken off from the tire wall or is the rim/tire going to be slightly taller?

[gotKRAUT]

as far as rims you are pretty limited on choices...BBS is the largest manufacturer of 3 piece wheels with "rims"....

if you are looking for wheels there is a much LARGER market out there to choose from

sorry im not really this big of an ass im just tired of the missuse of the term Rim

to answer the question, yes, when you go up a wheel size the sidewall of the tire must be shorter to keep the outside diameter of the tire the same as to avoid rubbing and speedometer issues