How to Read the Sidewall Information on Auto Tires

There is a wealth of information on the sidewall of auto tires. While you can learn a lot about the tires on your vehicle by deciphering the information, try to remember that the information on the tire is used as a guideline for the vehicle. Not all the information on the sidewall of the tire is what the vehicle manufacturers recommend on certain aspects of the tire.

Instructions

How to Read the Sidewall Information on Auto Tires

1. Locate the tire size, width, height, type, construction, load index, speed rating, and weather rating by the large number on the sidewall. For example P185/65/R15 88 H M&S would inform you this information as follows; P would indicate it's a passenger tire. Other letters used could be LT for light truck or T for temporary. 185 is the aspect ratio measured sidewall to sidewall in millimeters. 65 is the height of the tire in percentage to its width. R indicates it's a radial tire (other examples would be B for belted bias or D for diagonal bias). 15 stands for the diameter of the tire in inches. 88 is the load index displaying what the tire can carry at maximum inflation. H is the speed rating that the tire is designed to travel at. And M&S stands for mud and snow; another insignia would be a mountain and snowflake that would indicate a snow tire.

2. Find the DOT number on the sidewall of the tire. DOT numbers have a full display on one sidewall and a partial display on the other. Full DOT number would indicate the manufacturer and the plant that manufactured the tire in the first four digits after the letters DOT. The next three to four characters would be company specific information used in the event of a product recall issuance. The last four digits would be the date stamp of the tire. The first two digits of the date stamp would indicate the week it was manufactured and the last two digits would indicate the year it was manufactured. For example, 3407 would tell you the tire was manufactured on the 34th week of the year 2007.

3. Learn the maximum pressure and the maximum load of the tire in the small or "fine" print on the sidewall. Understand that the information on the sidewall of the tire is from the tire manufacturer and not always the recommended or same information listed by the auto manufacturer. In other words, you may have a P (passenger rated tire) that allows a maximum of 44 pounds per square inch of air inflation, but the auto manufacturer recommends no more than 32 pounds per square inch of air inflation for the vehicle. When it comes time for tire replacement, you can always upgrade to a higher rating tire, but you should never downgrade to a lesser tire than the manufacturer recommends.

4. Discover the quality rating of the tire (also in the "fine" print on the sidewall) in treadwear, traction and temperature. The higher the number in treadwear, the longer the tread should last. For example a 400 treadwear tire should last twice as long as a 200 treadwear tire. Traction would inform you of the stopping capacity of the tire on wet pavement. This is displayed in letters such as "AA" being the best, to "A," "B" and "C," being the worst. Temperature of the tire is again displayed in letters with "A" being the highest to "C" being the lowest. Since tires heat up while driving, this letter indicates the tire's ability to withstand that heat.