i've got a set of 18x7.5 rims with 215/35 rubber on my em1 2000 vtir coupe and it fits, although you may need to roll the guard to accomodate for the imperfections on the road if your car is lowered (i don't think a larger size would be recommended).

like VTEC16 said, it slows your acceleration considerably. although, on the other hand it has greater traction on the corners and in the wet.

good luck!