What rim size? with 15's, your limit is around 225/50 or 225/60. Same for 16". You can actually go larger with a 17" rim because the a-arm will go inside the rim instead of rubbing against it. A 235/40-50 will work here although I've read of guys going with 245's without too much trouble. Be careful of the backspacing. 4.5" is essential.