How to Read a Tire Sidewall

The markings on your tire sidewall contain a mix of letters and numbers. You can use the sidewall codes and values to determine a wealth of information about your tire. These alphanumeric markings can instantly tell you about the tire type, construction, size, and other features. Knowing how to read the sidewall codes can assist with easily describing a tire in detail.

P-Metric Sidewall Code

Your tire is P-Metric if the sidewall code begins with the letter "P". The P-Metric system became standard after being introduced by American tire manufacturers in 1977. It uses metric measurements and meets US-based standardized organization requirements.Below is an illustration of the a P-Metric sidewall code that shows what each character means:

The first character in a P-Metric code is a letter representing the tire class.

  • "P" designates a P-Metric passenger constructed tire built to US standards.
  • "LT" designates a light truck tire. LT tires are not part of the P-Metric family, but they are also built to US standards.
  • The absence of a letter indicates a passenger constructed tire built to European standards.

After the tire class, you will see a number representing the section width. This measurement identifies the tire width from sidewall to sidewall in millimeters.

  • The section width will be 3 digits.
  • Our example tire has a section width of 205 mm.

The aspect ratio follows the section width. It refers to the sidewall height as a percentage of the section width.

  • Find the aspect ratio by looking for the two-digit number after the slash.
  • Our example tire has an aspect ratio of 65 , meaning that its sidewall height is 65% percent of its 205mm section width.

Find the tire construction after the aspect ratio. This letter describes the tire's composition.

  • “R” stands for radial construction, where the tire’s plies run at 90 degrees to the centerline of the tread.
  • “D” stands for diagonal bias construction, where the plies are situated at angles lower than 90 degrees.

The wheel diameter is the last figure in a P-Metric sidewall code. It indicates the diameter of the wheel of which it can be mounted on. Our example tire has a wheel diameter of 16, meaning that it will fit on a 16-inch wheel.

Reading a High Flotation Tire Code

High flotation tires for light trucks feature a different sequence of letters and numbers on the sidewall.

Let's look at an example high flotation code:

High flotation codes begin by listing the tire's diameter, which is a measurement of the tire's height in inches.

  • The diameter will be a two-digit number.
  • Our example tire has a diameter of 35 inches.

Flotation codes next list the tire width, which is the width of the tire in inches.

  • The tire width will be a three or four-digit number with a decimal point.
  • Our example tire has a width of 12.50 inches.

Next, you will find a letter corresponding to the tire construction.

  • “R” stands for radial construction, where the tire’s plies run at 90 degrees to the centerline of the tread.
  • “D” stands for diagonal bias construction, where the plies are situated at angles lower than 90 degrees.

After the tire construction, the wheel diameter appears. It indicates the diameter of the rim of which it can be mounted on. Our example tire has a wheel diameter of 17, meaning that it will only fit on a 17-inch wheel.

Flotation codes end by giving the load range, which provides a comparative idea of the tire’s capacity to hold air and ability to carry weight.

  • Find the load range represented by a letter.
  • Our example tire is rated in load rangeE.

Learn more about Load Ranges.

Other Sidewall Markings

In addition to the size codes, your sidewall contains other markings that provide even more information about the tire’s characteristics. Reading these markings gives you extra information about the tire’s age, construction, performance attributes, and more. Let’s look at some of these other markings to figure out what they mean.

Load Index and Speed Ratings

After the size code, you will find characters representing the tire’s load index and speed rating:

The load index is a number explicitly indicating how much weight your tire can carry at different inflation pressures. You can find this number in the load index table, where it refers to your tire’s carrying capacity in pounds. Our example tire has a load range of 92, which corresponds to 1389 lbs at 36 psi.

Learn more about Carrying Capacity.

The speed rating is a letter indicating the maximum speed that a tire can safely reach and maintain, as determined by laboratory testing. Here, the example tire has an “H” speed rating, which means it can safely travel at speeds up to 130 mph.

Learn more about Speed Ratings.

US DOT and Safety Standard Markings

The Department of Transportation and safety markings provide information about your tire’s creation and its compatibility with federal regulations. You will see these figures stamped on the sidewall in a sequence that looks similar to the size code. The DOT and safety markings look like this:

The DOT designation indicates that the tire meets or exceeds the U.S. Department of Transportation's safety requirements for on-road use. Tires without this designation should not be legally driven on US public roads.

The plant code appears as the two letters after “DOT.” These characters identify the tire’s manufacturer and site of creation.

After the plant code, you will find two characters that express the tire size in a code determined by the manufacturer.

The first three characters after the dash represents brand characteristics in a code also determined by the manufacturer. The plant code, tire size, and brand characteristics are intended for the manufacturer’s internal use.

After the brand characteristics, there are four numbers representing the tire’s date of creation. The first two numbers in this sequence tell you the tire’s manufactured week.

  • The manufactured week identifies which week of the year the tire was made in.
  • Our example tire lists 10 as it’s manufactured week, so it was produced in the 10th week of the year.

The Manufactured Year is represented by the last two of the four digits .

  • The manufactured year identifies the year the tire was produced.
  • Combine the manufacture week and year to determine exactly when the tire was made.
  • Our example tire lists 10 as its manufactured year, so it was made during the 10th week of 2016.

Treadwear, Traction, and Temperature Markings

In addition to safety and manufacturer information, the DOT stipulates that all tires display their performance grades under the Uniform Tire Quality Grade (UTQG) system. This system provides a comparative measure of the tire’s ability to resist wear, hydroplaning, and heat buildup. The UTQG markings are spelled out, like this:

The treadwear grade appears first. It offers a relative score describing a tire’s ability to resist wear.

  • The treadwear grade comparatively assesses wear resistance among tires made by the same brand.
  • Our example tire’s 520 treadwear rating places it in a numerical context along with others made by the same manufacturer.
The traction grade appears next. This ranking describes the tire’s ability to stop on straight, wet surfaces under controlled conditions.

  • Traction grades are given on a comparative scale: AA, A, B, and C. The highest is AA; the lowest is C.
  • Our example tire has an “A” traction grade, meaning that it has very good but not superior stopping power on wet surfaces.
The temperature grade is the sidewall’s last UTQG marking. It describes the tire’s ability to dissipate heat and resist temperature buildup.

  • Temperature grades are also given on a comparative scale: A, B, and C.
  • Our example tire has the highest temperature grade, an “A.”

Learn more about Treadwear, Traction, and Temperature Ratings.

Maximum Load Capacity and Inflation Pressure

Along with its size codes and performance grades, your tire sidewall also displays the tire’s maximum load limit and inflation pressure. You’ll see these specs explicitly called out:

The maximum load capacity, like the load index, identifies your tire’s load carrying capacity when inflated to its maximum air pressure.

The maximum air pressure represents the tire’s maximum operating inflation pressure.

  • Standard and extra load tires meet the maximum load at 36 and 42 PSI, respectively, and maintain that load up to the tire’s maximum operating inflation pressure.
  • The example tire has a maximum pressure of 44 psi.
  • Remember that these maximum load and air pressure limits apply to the tire and not your vehicle. Always check your owner’s manual for your vehicle’s cold inflation pressure recommendations.

Ply Construction

Additionally, your tire sidewall will display information about its construction. You will find this information written out in a clear format:

This information tells you which materials are used in the tire’s plies, and the quantity of each type of ply.

Learn more about Tire Construction.

Rotation Direction

Some tires are designed to be installed in a specific way. In these cases, look to the sidewall for instructions regarding the tire’s correct position. There, you will find directions for the tire’s correct mounting and installation:

Directional Tires have a specified direction of rotation. These tires feature arrows on the sidewall indicating the direction they should rotate.

Asymmetrical Tires have different patterns on the outside and inside halves of the tread. They will have the word “outside” labeled on the side of the tire that should face outward.

Some tires are both directional and asymmetrical. These tires will indicate both the proper direction of rotation and the outward side.

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