I am about to put some old RS wheels (16x7) with 225-45-16 tires on my wagon. This will be my first upgrade from the stock tire size, so all of my info I have heard second-hand, but there is a wagon suspension thread, talks mostly about lowering problems, but its good to know.
See the other threads up right now, some are saying 235 width will work as well, that would be cool! I am staying 225 for AutoX classing.