Tire Diameters: Understanding

Standard wheel menu

The library of standard wheels in BikeCAD serves as a good reference for the tire diameters of numerous standard tires. These diameter values have been determined by physically measuring numerous sample wheels. It should be understood that actual wheel diameters can vary greatly between different tire brands and models. When in doubt, be sure to measure the diameter of the wheels you plan to use.

It has sometimes been assumed that one should be able to calculate the wheel diameter from the published ISO bead seat diameter of the rim and the published width of the tire. For example, a 700c rim has an ISO bead seat diameter of 622 mm. If that rim is fitted with a 700 x 23c tire, some have assumed that the overall diameter of the wheel would be 622 mm + 2 * 23 mm = 668 mm. While this sort of makes sense, it just never seems to work out. Remember, the tire company only publishes the width of the tire. (It should be noted that even the published width dimension does not always accurately reflect the true width.) And of course, the height of the tire may be different than the width.

Again, when in doubt, measure your own wheels!