Making an attempt at trying to decipher the codes on the sidewall of a tire can be like reading a foreign language. There are a lot of considerations past the actual tire making process that is required to properly identify a tire. However, it is important information that must be used to make sure that you get the right tire and of course for tire safety purposes as well. If you look at the side of the tire you will see a series of numbers, they might look something like this, P225-60R16 97H M+S
The list below explains each letter / number:
• P = Passenger car tire
• 225 = width of tire in millimeters
• 60 = aspect ratio, or ratio of tire width to tire height
• R = construction, Radial
• 16 = rim diameter code
To the right of that code, there may be load and speed rating, for example as noted above: 97H M+S
• 97 = load index
• H = speed symbol
An M + S indicates that the tire is rated for heavy snow and ice conditions.
The last part of the information is the Uniform Tire Quality Grade System (UTQGS) rankings: traction (AA, A, B or C), temperature (A, B or C) and tread wear (usually from 100 to 800). Then the manufacturer and the tire name (ex. Michelin) will also be affixed to the outer sidewall in tall block letters. There is more information about the tire on the inner sidewall near the rim such as the maximum allowable inflation pressure, in PSI (pounds per square inch). This information should also be listed inside the driver side door.
More information is still present but might not as useful to you; on the rim you will find the DOT identification number, tire composition materials and maximum load rating. The DOT identification number is usually 12 characters long and includes the date of manufacture on the end. So a 1308 would specify that the tire was made in the thirteenth week of 2008. This is a US Government system that allows you the ability to compare tire for a number of different things such as traction, tread wear life, heat, performance on road and weather conditions, vehicle weight, and inflation pressure.
Other terms that you might want to familiarize yourself with are tread wear grade, traction grade, and temperature grade. Tread wear grade measures the tread wear life and gives you the capability to compare tires tht have the same manufacturer. The higher numbers indicates the longer a tire is expected to wear. If you see this number and it is a 400 then it would make sense that it would last twice as long as a number 200. You should note that these numbers are not always standard. Traction grade measures the tires ability to stop, higher letters are best. Temperature grade is the ability of the tire to perform in hot weather; again a higher number is best.
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