Yeah...a 16" 5.5" wide car tire, the kind that would fit on the back of a shovel. People who have never done it claim you will die immediately if you run a car tire on a bike; you'll go into a turn and just explode in flames. The Goldwing and Harley guys over at darkside.nwff.info (where they specialize in such things) feel differently. The shovel wears them all square anyway, so why not get car mileage in the meantime?
I'm dying to try it out. Just don't ride behind me if I do it, mmmkay?