What Do Tire Size Numbers Mean?


Quick Answer

Tire size numbers, located on the sidewalls of all tires, provide information such as what class of vehicles tires are suited for, maximum load, tire width and more. Tire size numbers appear in a series of letters and numbers, which varies among different types of tires and brands. Regardless of number pattern, however, all tires follow a standard format, helping drivers identify the best tires for their specific cars.

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What Do Tire Size Numbers Mean?
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Full Answer

Tire size information generally begins with a letter or pair of letters, which indicates vehicle type and class the tires suit. Categories include passenger vehicles, vans and trucks. Some tires appear without letters, however, indicating production in Europe. In addition to appropriate size, the class of vehicles tires suit best inflate to different volumes according to class. Tire width follows, appearing in three numbers that measure tire diameter in millimeters. The aspect ratio comes next, indicating the tires' height to width measurements. Construction type of the tires follows, and indicates tread direction. The wheel diameter appears in inches as the next number, letting drivers identify the proper wheel size. Load index follows, indicating maximum weight tires can carry. Next, a speed index indicates maximum safe traveling speeds. A series of letters (DOT) should follow, indicating tires conform with federal regulations. Next, tires bear a distinct identification number, or TIN, which shows the time and place of production. Tires then display a traction grade, showing performance with "A" as the best and "C" the worst. Lastly, a temperature grades show anticipated tread wear rate.

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