Here's how I'm storing my wheels and tires these days. They are just cheap shelf brackets from the hardware store. Biggest one they sell, 16" I think. I bent the end up slightly, so a wheel/tire can't accidentally slide off. Buy them by the box, screw them to the wall and there ya go. So far, I'm pretty happy with this set-up. If I need something at the back of the stack, it's not so deep that it's too much trouble to retrieve. I'm thinking about putting an inverted hook on the end of a shovel handle, so I can get them down without getting out the ladder.
