Wheel Sizes

I just recently purchased a set of 18'' rims for my 1999 Grand AM SE2 and I noticed that there is still kind of a lot of tire left. I was wondering would 20'' wheels fit on there with a 30 or 35 series tire, because I have a 40 series on there with the 18's. Sorry if this has been asked a million times.

I think your biggest concern will be comfort if you go to a 20" wheel. Plus the shorter your sidewalls get the harder it becomes to feel when your tires are about to lose traction during hard cornering. I personally wouldn't go over 17" for good performance. This is my opinon though, but 20's do look pretty sweet.