What Do Automobile Tire Sizes Mean?

If you're looking at tires in an auto parts store, you can decode the tire size and other information from the numbers and letters printed on the tire. Analyze a hypothetical P195/60R15 89H tire to learn how to make sense of the data.

Tire Class and Section Width

The letter P signifies that the 195 is a metric measurement. It means that the tire is 195 millimeters wide at the widest point, or roughly 7.67 inches.

Aspect Ratio

The number following the slash is always a multiple of 10, and it is the ratio of the distance between the rim and the ground, compared to the tire width. A lower ratio means a lower profile tire.

Radial and Wheel Diameter

Almost all new tires will have an "R" because of their radial construction. The number following it is the diameter of the rim for which the tire is designed, in this case 15 inches.

Load Index

This is the load that each tire is designed to carry. In this case, 89 corresponds to a load rating of 1,279 pounds. Higher numbers mean that a tire can handle more weight in standard driving.

Speed Rating

No roads in the U.S. have speed limits above 75 miles per hour, but tires must be tested for maximum speed thanks to the German Autobahn. For this tire, an H rating means a maximum speed of 130 mph.

References

• Discount Tire Direct: Explanation of Sidewall Markings
• TireRack.com: Description of Sidewall Terminology