How to Determine Motorcycle Tire Size

Motorcycle tires, like motorcycles themselves, come in many types and sizes. There are different types of tires for front wheels, back wheels, off road, street and racing motorcycles. Choosing the correct size of motorcycle tire is essential because using the wrong size can potentially be deadly. Motorcycle tires are measured using either the English or metric systems, although metric is usually used. The height, the width and the rim size of the tires all must be correct for the particular motorcycle and are included in the tire's size code.

Difficulty: Easy

Instructions

Things You'll Need:

• Motorcycle tire Tape measure

1. Determine the section width in millimeters. This is the maximum horizontal distance across the tire's cross section. This will be the first number in the tire's size code.

2. Measure the maximum cross section height in millimeters. This is the maximum vertical distance in the tire's cross section. This number is not found in the tire code, but is needed to calculate the second number in the code.

3. Divide the cross section height by the cross section width and multiply the result by 100. This is the aspect ratio given as a percentage and is the second number in the size code. A tire with a size code of 130/90 has a cross section width of 130 mm and a cross section height of 117 mm (0.9 * 130 mm).

4. Measure the diameter of the rim diameter in inches. This will be the fourth entry in the size code. There is a speed rating entry that is the third space in the code, but this has little to do with size determination. A motorcycle tire with a size code of 130/90 H 16 will have a cross section width of 130 mm, a cross section height of 117 mm and a rim diameter of 16 inches. It would also be rated for 130 mph.

Tips & Warnings

• Rarely will you find size codes in English units. These codes do not use an aspect ratio to calculate cross section height. It is either stated explicitly or left out completely.

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