I love this idea. Since this is my first GW I have never heard of using a car tire on a bike before, except for the old Boss Hoss I rode back in the 90's. That was a large tire. It was still maneuverable although a little slow in the turns. No worse than a 250-300mm bike tire. How do you decide the car tire size and will anyone install them? I guess I'll check out the dark side forums too.