You can accurately measure wheel rim and overall rim width by starting and stopping the measurements in the right place each time. When replacing rims or tires, it is important to know what size rim you have. Wheel rim width is taken two different ways to fully describe the dimensions of the inside and outside edges.
Set the empty rim up vertically on a soft towel in a flat and well-lighted area.
Measure the rim from the inner edge of one lip, where the sidewall of the tire would rest, straight across to the inner edge of the other lip. The distance between these two inner edges is simply called the rim width, as it does not include the thickness of the rim lips.
Take a second measurement from the outer edge of one rim lip, where the sidewall of the tire would rest, straight across to the outer edge of the other lip. The distance from the two outer edges is known as the overall rim width.
