blue660r01

Quick explanation I pulled up since Im too lazy to type it ...


On the side of every tire is a host of numbers and ratings that describe the tire and its performance characteristics. A typical tire size numbering system will appear as a string of letters and numbers, such as this example: P215/70R16 100S

P215/70R16 100S

The first digit in the tire size indicates the type of tire and intended use. In this example, the first digit is “P” which indicates the tire is a metric size, used primarily on passenger vehicles. Other letter designations include T (Temporary Spare), LT (Light Truck Metric), C (Commercial), and ST (Special Trailer Service).

P215/70R16 100S

The following numbers before the slash (/) indicates the section width of the tire; the widest point from sidewall-to-sidewall. The larger this number, the wider the tire. This number is the wide of the tire in millimeters. In this example, the tire has a 215-millimeter section width.

P215/70R16 100S

The next number trailing the slash (/) indicates the height of the tire in a percentage of the section width. In our example, the number is 70, which means the tire height is 70% of the section width, which is 215 millimeters. The height of this tire would be 150.5 millimeters. The lower the number is, the lower the profile of the tire.

P215/70R16 100S

The next letter is reveals the construction of the tire. The most common is “R” such as found in our example. The “R” designation states the tire is of radial construction. Other construction types are rarer for modern passenger car use, and may include “D” for bias ply construction and “B” for belted tires.

P215/70R16 100S

The number following the construction code is the size of the wheel in inches. The example tire would be designed to fit a 16-inch wheel. Tire sizes on modern vehicles typically start at 13-inches and go up to 18-inches, but aftermarket and special package wheels can be 22-inches or even larger.

P215/70R16 100S

Usually following the tire size information is the tire performance information. The first number, in this case “100” designates the load carrying capacity of the tire. This particular example would be rated for 1,764 pounds. Load ratings generally start at 71 (761 pounds) and go up to 110 (2,337 pounds) for passenger vehicles.

P215/70R16 100S

The final number in the tire performance rating is the speed rating. In this example the speed rating is “S.” This tire would be rated for 112-mph. Speed ratings start at M (81-mph) and go up to Y (186-mph). If a tire is rated Y but the rating is enclosed in parenthesis, this means the tire has been tested at speeds greater than 186-mph. If our example tire was rated 100Y and tested faster than 186-mph, the performance number would be (100Y).