1. Tire Width. The width of the tire measured in mm from sidewall to sidewall. The tire width in the above picture is 205 mm.

2. Tire Profile. The tire profile is the ratio of the height of the tires cross-section to its width. On our example, 55 means that the height is equal to 55% of the tires width.

3. Rim Diameter. The rim diameter is the width in inches or cm of the wheel from one end to the other. The diameter of this wheel is 16 in. Always replace a tire on a rim with another tire of exactly the same rim diameter designation and suffix letters.

4. Speed Rating. The speed rating tells you the maximum service speed for a tire. A speed rating is not, however, a recommendation to exceed speed limits, and does not indicate how well a tire handles or corners.