The ones I'm using are 31x10.5x15... instead of using the stock 15x7
inch wheels, I [after looking for about 6 months] got rally/factory 15x8
inchers; to give extra width, traction, and a flatter footprint. I've
noticed over the years, doing similar allows a little extra air to be
used without causing that hard bouncy ride, you get when using narrower
wheels. Using a wider wheel, I'm able to run about 35-36lbs in mine...
and they perform very well.