Rims and Tires Plus sizing

Calculating tires dimensions

1. Width X aspect ratio = section height.

2. Section height X 2 = combined section height.

3. Combined section height + wheel diameter = overall tire diameter. Example: 185/60R14. 1. 185mm X 0.60 = 111mm (section height).

2. 111mm X 2 = 222mm (combined section height).

3. 222mm + 355.6mm = 577.6mm or 22.74 inches (overall tire diameter). When reading a tire size, the first number represents the section width in millimeters.

To convert millimeters to inches, divide by 25.4.

The second number represents the aspect ratio. This is a ratio of sidewall height to section width. In the example (courtesy of The Tire Rack), the tire is 7.28 inches wide. By multiplying section width by the aspect ratio, you can determine the height of one sidewall. So, in this example, 185 X 0.60 = 111mm sidewall height (in inches: 7.28 inches X 0.60 = 4.36 inches).

To determine the outside diameter of a tire, multiply sidewall height by two and add wheel diameter. For example, if the individual sidewall height is 4.36 inches: 4.36 inches X 2 = 8.72 inches.

By adding 8.72 inches to the 14-inch wheel diameter, the tire's overall diameter should be 22.72 inches.