I'm looking at some new wheels and tires for my 2000 Base Cavalier. I have a friend who has some 18x7.5 wheels with low low profile tires. What is the max. wheel size I could have without any problem on my car.

19"
I have 18x7.5 also

you can a 20'' on the back , and some one told me u can get a 20 on the front if u can find a set 7-7.5'' wide.

with mods to the fender walls and stuff... and really low profile tires