Originally Posted by Crankycrank

29" is the same as 700c which is actually 622mm diameter. To make things easier, go by the "ISO" rating listed on most tires along with some other measuring systems. ISO gives you in millimeters the diameter and width of the tire. Here is a loooong article explaining everything but not necessary to read the whole thing as it gives comparison charts to the different sizing systems used in the world. So a 29" x 2" would be an ISO of 622mm x approx 50mm.Tire Sizing Systems (sheldonbrown.com)