What Does 90 90 21 on My Motorcycle Tire Mean?

The numbers on a motorcycle tire indicate the width, aspect ratio, and rim size of the tire. For example, a motorcycle tire with the numbers 90/90-21 means that the tire is approximately 90 centimeters wide and has a sidewall height that is 90% of the tire’s width. The last number indicates the rim size in inches.

The aspect ratio is the second number in the series and represents the height of the tire’s sidewall as a percentage of the tire’s width.

The larger the aspect ratio number, the taller the tire will be. For example, a tire with an aspect ratio of 90 will have a taller sidewall than a tire with an aspect ratio of 70.

It is important to note that the speed rating and construction of the tire may also be indicated by letters mixed in with the numbers.

The speed rating indicates the maximum speed that the tire can handle, while the construction indicates whether the tire is bias-ply or radial.

In summary, the numbers on a motorcycle tire indicate the width, aspect ratio, and rim size of the tire. The aspect ratio represents the height of the tire’s sidewall as a percentage of the tire’s width.

The speed rating and construction of the tire may also be indicated by letters mixed in with the numbers.

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