Tires are measured and classified by their dimensions, which tell you about the tire’s size. These dimensions are expressed in various measuring units such as millimeters, inches, and percentages.
The various units help tire experts precisely discuss or classify tire and wheel dimensions. You’ve likely already encountered tire some dimensions in the tire size code. The section width, aspect ratio, and rim diameter all make up the tire size code. Below are a few more examples of dimensions when it comes to tires.
- Section Width
- The distance between the outer sidewall’s widest point and the inner sidewall’s widest point. This physical width of the tire can change if the tire is mounted on a wheel slightly wider or narrower than the size indicated by the rim width. Section width serves as the first number in a metric tire size code.
- Overall Width
- The measurement of a tire’s width from sidewall exterior to sidewall exterior, including any features molded on to the sidewall’s outside. Overall widths pertain mostly to tires with decorative whitewalls on the sidewall exterior, or to off-road tires with rim protectors.
- Tread Width
- The distance between the two outer edges of a tire’s tread.
- Rim Width
- Describes the acceptable range of wheel widths approved for a particular size of tire.
- Section Height
- The distance between the top of the tire tread and the bottom of the tire bead. Tire fitment experts use this measurement to determine the aspect ratio, which helps them determine if certain plus sizes can be mounted on a given vehicle.
- Overall Diameter
- Measurement of a tire’s outside diameter through its exact center when inflated with no load.
- Rim Diameter
- The distance between the bottom the bead seat area, directly across from each other, on the same side of the wheel. This is used to ensure a matching wheel diameter is compatible with the tire. Rim diameters start at four inches.
- The 360 degree distance around the outside of the tire tread. Fitment experts use the circumference to calculate the number of revolutions per mile.