I have a 00 S4 stock with the exception of my Borla cat back and my question is how do they measure the size of the wheel, Do you measure it from lip to lip on the outside or the diameter of the inside of the wheel? I was just curious because because I just went outside to measure and see how big my wheels were, well from lip to lip outside they measure 18.5 minus rubber and around 23 with rubber, and i thought the stock wheels were 17" but like i said I dont know how they measure.

 

Stock wheels are 17" but they do make one that look the same in 18", definitly not 18.5 though haha. Generally you dont measure your wheels like that with a measuring tape... The way the rubber fits onto the wheel probably messes it up a bit. Your tires should say the wheel size. 225/45/17 or something like that.