Shopping for tires, we'd heard good things about the Mickey Thompson tire line, so we checked out the sizes available using the net. We don't know why they do this, but tire manufacturers offer a nominal size and then build them to a different size. For example, our old Firestones, listed as "11.5x29.5x15" actually measured 12x30x15-inches. M/T P/N 3064, with an 11.1-inch actual tread width and 29.9-inch diameter, was the closest we could find. When we went to order them, the factory recommended that we consider the 3062W because it had a thicker sidewall better suited to our heavier car, but we didn't notice that 3062Ws were a shorter tire, 29.6-inch overall diameter, as opposed to the 3064's 29.9-inch O.D.