Wondering the age or size of your tires? The sidewall of your vehicle’s tire has all the answers you’re looking for! We realize the blizzard of numbers, letters and words just look like hieroglyphics but they’re easy to understand with a little explanation.
In this article we’ll discuss where to read tire codes and what each of the letters or numbers mean.
Where To Read Tire Codes?
To read your tire code, look near the edge of the rim for a series of characters starting with the letters DOT. DOT refers to the Department of Transportation, indicating that the tire has passed all the minimum standards set by the DOT for the sale of tires in the United States.
The code on the tire can tell us about the manufacturer, which factory it was made in, and details about that lot so that they can track them in case of a recall.
The last four digits tell us about when the tire was manufactured:
- The first two numbers of the code indicate which week of the year the tires were manufactured
- The last two digits reveal the year of manufacturing
Here’s an example: 2821
- 28 means that it was manufactured during the 28th week of the year
- 21 means the tire was manufactured in the year 2021
Note – This information is not relevant for any tires manufactured before the year 2000.
101 In Reading Tire Codes
Service Description – It is the first letter of the code which indicates the tire type. Here are the most common codes:
- P – Passenger car
- LT – Light truck
- ST – Special trailer
- T – Temporary
- M + S – Mud and snow
Tire Width – The first number in the code refers to the tire’s width i.e distance from one sidewall edge to another. It is displayed in millimeters (mm).
A larger number means a wider tire.
Aspect Ratio – It refers to the height of the tire sidewall corresponding to the tread width. For example – 65 in the picture above indicates that the size of height is 65% the width of the tire.
Construction – The letter following the aspect ratio refers to the construction of the tire. Most tires sold today are of radial construction i.e R. The other lesser common codes are D for diagonal and B for bias belted.
Wheel Diameter – The number following the construction code refers to the size of the wheel (in inches), on which the tire will be mounted. In the example above, you can see the size of the rim is 15 inches. Hence, the tire will be mounted on a 15” wheel.
Load Index – One of the most important codes that signify the tire strength is a Load Index. This number indicates the maximum load that the tire can carry when fully inflated. You can refer to the Load index chart below for details.
Speed Rating – This letter next to the load index represents the max speed capability of the tire.
Refer to the speed rating chart below:
The Department of Transportation also requires the manufacturer to grade its tires under the Uniform Tire Quality Grade (UTQG) standards.
These values determined by the manufacturer establish the ratings for traction, treadwear and temperature resistance.
Traction – The traction rating refers to the tire’s ability to stop in a straight line on wet asphalt and concrete under the controlled conditions of a test track. The traction grades are AA, A, B or C, with AA having the best stopping ability out of all.
Treadwear – The treadwear grading is based on the rate of wear a tire displays during a 7,200-mile on-vehicle test. The higher the number, the longer the tire will likely last. For example, a treadwear value of 550 should deliver more mileage than one of 300.
Temperature – The temperature rating refers to the tire’s resistance to heat when driven at high speeds. The grades vary from A to C.
Reading Tire Codes Video
We realize this is a lot to read and process so here’s a video that also breaks down the tire codes:
