Tire Size Question

If you're planning on doing any sort of off roading, a poke in the tire won't save your wheels. You'll want to switch to a smaller wheel for better protection. Smaller wheels also allow for bigger tires and thus better grip. A general rule of thumb for off roading is your tires should be about twice the size of your wheels. That's not going to be possible at any compatible wheel size with the Atlas Cross Sport (unless you get a serious lift kit installed), but you're certainly going to get closer with 31" tires on a 17" wheel.