I have 31 X 10.50 15" on a 2wd and they have room to grow. These came stock on the 4wd models. But an easy way to find out is to call a local shop and they can give you a plus size. I used to have some 20"ers and they rubbed on the valence... but an easy fix if that's the case is to just cut the valence at an angle. A utility knife will fix that. And it really doesn't affect the looks at all, you can hardly tell it's not stock.Are 32"x11.5" tires going to rub on a stock truck with some slightly off set 15" rims?