I run 31x10.5 R15s on my stock setup with no trubble, I have heard of bigger but the real issue is back spacing. Wider tires are more likely to rub. I read somewhere on here that a guy put 35x10.5s on a stock height rig just to show it could be done, he said it had "minimal rubbing" what ever that meant. I believe you could pull off 32s