Originally Posted by Lothos
FWIW, tires diameter sizes are measured unmounted when listed to ensure air pressure and rim selection do not pose a factor in the measured size of the tire. They are also measured at room temperature since it can play a major role in the measurement of rubber especially when you get to very larger tires.
Did anyone see mythbusters on pikes peak? They had 5 miles of matchbox car track laid out and as it warmed it stretched another 2 miles in length?
Also, tires get bigger when you mount them... they aren't measured unmounted...