by Joseph Hazelbaker

Created on: March 25, 2007   Last Updated: April 10, 2007

If you noticed all the embossed writing on the sidewalls of your tires, you were probably looking for either the recommended tire pressure range or the tire size. You may have been surprised and confused by all of the other number and abbreviations you had to sort through to get at that important information.

Here's a guide to help you decipher all that code and determine what you need to pay attention to and what you can ignore.

What you need to look for is a series of seven or so numbers with one or two letters and a forward slash followed by a space and another series of three or four numbers and letters. The numbers and letters won't be the largest on the tire (they save that to advertise their tire name, of course), but they won't be the smallest either.

On one of my vehicles the sequence is:

225/65R15 102T

On another vehicle, the sequence is:

205/70R15 96T

Your tires might contain the sequence that starts with a letter or two. For example, using the first sequence from above, your tire might say:

P225/65R15

The first letter or two is the abbreviation for the tire description (e.g. "P" for passenger, "T" for temporary, and "LT" for light truck). As you can see from my two sequences, not all tires carry such a description.

After the letter(s), the first set of numbers (e.g. "225" or "205" above) refers to the tread width in millimeters. The higher the number, the wider the tire. So my two tires are 225 millimeters in width and 205 millimeters in width respectively.

The forward slash simply separates the first set of numbers from the second set.

The number immediately to the right of the forward slash is the Aspect Ratio, or the ratio of the sidewall height to the tire width. It is presented as a percentage. For my tires, 65% and 70% respectively.

The next letter is an abbreviation for the type of tire. "R" stands for radial and most tires are radials.

The next number represents the diameter of the wheel (not the tire). In both my sequences above, both tires are made to fit a 15-inch wheel.

That ends the first part of the sequence. A space will follow and then a another number called a "load index" which indicates how much weight your tire can support. This will be a two or three-digit number. In my first sequence, this number is "102" and it means that the tire can carry about 1800 pounds. You really don't need to know this number as it will likely be stated elsewhere in an easier to read format such as "max load 850 kg 1874 lbs.", which is exactly what my first tire

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