I dont think they make 31/11.5s unless its a swamper. Usually it's 10.5 wide. My 32's fit just fine. There is a lack of suspension travel for off road use but I think the suspension bottoms out before it hits the fender. I've gone off roading, over rocks and boulders and havn't had a problem. It will rub a small amount when the steering wheel is at full lock on the radius arm. However, it's not a big deal and you're not suppose to turn the wheel against the steering stops anyway.