I have run a few auto tires on the rear of the bike when a sidecar was on it. It is difficult to get the tire to set the bead on some bikes. I have successfully done them on Suzukis with a 15 inch rear wheel. I got more than 20,000 miles on the rear tire compared to 3,000 to 6,000 for motorcycle tires. It had better rear wheel braking
power and got better miles per gallon too. Steering was also better. There is a slight discrepancy in the 15 inch rims that may make some tires impossible to get
the bead on.