Tire Sizes

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Tire Sizes

The size of most tires for both passenger vehicles and light trucks are represented by a combination of numbers and letters that are printed on the sidewall of your tires.

Original Equipment Approval Code

All tires must have a DOT, Department of Transportation numbers which indicate that the tire has passed all minimum DOT standards.

Uniform Tire Quality Grading (UTQG) Marking

The Department of Transportation requires each manufacturer to grade its tires under the Uniform Tire Quality Grade (UTQG) labeling system and establish ratings for treadwear, traction and temperature resistance. These tests are conducted independently by each manufacturer following government guidelines to assign values that represent a comparison between the tested tire and a control tire.

Section Width

Section Width is the width of the tire from one sidewall to the other sidewall in millimeters. This tire in the example above is 225 millimeters wide.

Aspect Ratio

Aspect Ratio is the ratio of the sidewall height to the section width. The sidewall height of example tire above is 50% of its section width.

Wheel Diameter

Wheel Diameter specifies the size, in inches, of the wheel that a tire fits. The example tire will only fit a 16-inch wheel.