they'll fit, but the sidewalls will be at like 45-degree angles...if you're worried about performance, get smaller wheels, 18s arent helping much. but yeah, ideally you'd have 225s or 235s for 8"-wide rim...

also, check to make sure your toyos will even fit on 8" wide rims...I've seen some 225s that could fit 7"-wide rims, and some that couldn't...they're all made differently, so look into that