Reading Your Tire's Sidewalls
Your tire’s sidewall is the outer and inner “walls”, located on the sides of a tire. Every tire’s sidewall features unique information that is divided into two distinct sections.
Outer Rim Information
Tire Specs (Tire Size)
Tire specs describe the fundamental characteristics of the tire itself. This includes, speed rating, size, construction, etc. More specifically:
- Tire type
- Tire width
- Aspect ratio
- Wheel diameter
- Speed rating
- Load index
See our Tire Size article for a more in depth explanation of tire sizes.
Tire type refers to the type of vehicle the tire fits. P stands for passenger metric. You may encounter other signifiers like LT, which stands for light truck, T for temporary spare, and ST for specific trailers. If your tire does not have a letter, it means that it’s a Euro or metric size (See diagram A).
Uniform Tire Quality Grading
Your tire will also have a Uniform Tire Quality Grading (UTQG) code. This was established by the National Highway Safety Administration (NHTSA) to test tires under government-prescribed test methods. Each tire is graded on three main components including:
- Treadwear. This indicates the wear rate of the tire, comparable to other tires within a manufacturer’s line. By these standards, a tire with a 100 rating is the baseline grade. A tire with a rating of 200 could last twice as long compared to a tire that bears a rating of 100.
- Traction. Grades for this category are AA, A, B, and C. AA is the highest rating. These grades represent the tire’s ability to stop straight on wet pavement, as measured by the specified government track. Tires rated under grade C are unacceptable for road travel.
- Temperature. Temperature grades are rated A, B and C, with A being the highest and C representing the lowest. These indicate the tire’s ability to dissipate heat under controlled indoor test conditions. Tires that are related below grade C are considered unacceptable for use. (See diagram A)
Some tires have unique features, and these features are showcased with unique icons. The letters M and S (M+S) indicate that the tire complies with the Rubber Manufacturers Association’s standards for a proper mud and snow tire. Letters can be found in the following combinations: M/S, M+S, and M&S, and all-season tires bear this mark.
Outer Rim Information
Department of Transportation Safety Code
Your tire will have a Department of Transportation(DOT) Safety Code, which assures that your tire complies with all DOTstandards. You’ll find the DOT insignia within your tire’s identification number, which begins with the tire’s manufacturer and plant code – identified by two numbers or letters. The ninth and tenth characters of this code specify the week the tire was manufactured, and the final numbers signify the year the tire was manufactured (see diagram B).
Maximum Cold Inflation & Load Limit
The number listed here indicates the maximum amount of air you can put in a tire before it becomes overinflated. It is not the recommended tire pressure. That number will be in your owner's manual (see diagram A).
Maximum Load Limit
This number indicates your tire's maximum load-carrying capabilities when the tire is inflated to its maximum inflation pressure, as indicated on the sidewall (see diagram A).
Tire Ply Composition & Materials
This information tells you what materials are used in your tire's plies, and the quantity of each type included (see diagram A).