Wheel bearings can wear out differently with much larger tires, but 31's aren't big enough to affect them too bad. Stock bearings last a very long time with stock sized tires, but with oversized tires, they won't last as long anymore. I had a sami with 33's and the rear wheel bearings did give me some problems. That was before i found out the housing was slightly bent, causing the bearings to run at an off-angle.