TIRES 101: READING A SIDEWALL

The sidewall of a tire includes a variety of important information. The numbers and letters identify dimensions and performance standards that allow you to compare tires more accurately and efficiently. This diagram will help you to understand those numbers and letters. For assistance in selecting a replacement tire, always consult your Toyo Tires dealer.

 

LOAD INDEX
& SPEED SYMBOL

The load index number and speed symbol correspond to the maximum load-carrying capacity of the tire and its maximum speed capability.

The load index number and speed symbol correspond to the maximum load-carrying capacity of the tire and its maximum speed capability.

The load index is an assigned number that corresponds with the load-carrying capacity of the tire. For example, "96" indicates a load-carrying capacity of 1565 lb at maximum inflation pressure. The load index for most passenger car tires ranges from 75-100.  Click here to view the complete load inflation index.

Load Index Chart

Load index chart

Speed ratings are determined by indoor laboratory testing methods, which measure high-speed tire durability under controlled test conditions. These test procedures do not take into account underinflation, tire damage, vehicle characteristics or road conditions which can lead to sudden tire failure or loss of vehicle control at much lower speeds than indicated by the tire's speed rating.

Speed Symbol Chart

speed symbol chart

When replacing tires on your vehicle, you should use replacement tires with a speed rating equal to or greater than that of the original equipment tires if the speed capability and handling characteristics of the vehicle are to be maintained.

Remember to never operate your vehicle in an unsafe or unlawful manner. Your Toyo Tires dealer can provide you with more information on speed ratings.

DIAMETER

The diameter is the size of the wheel from one side to the other.
Diameter The diameter indicates the size of the wheel from one side to the other.. You can learn more about changing the diameter of the wheels of your car in the Plus Sizing section.

RADIAL

Tires with an "R" indicate radial tire construction.

The "R" stands for "radial," indicating the tire has radial construction.

ASPECT RATIO

The aspect ratio indicates the dimensional relationship of the section height to the section width.

 

Aspect Ratio The aspect ratio is the dimensional relationship of the section height to the section width. The lower the aspect ratio, the shorter the sidewall and the wider the shoulder-to-shoulder width.

WIDTH

The width indicates the widest point of a tire from sidewall to sidewall.
Width 

The width of a tire is referred to as its section width.  The width indicates the widest point of a tire from sidwall to sidewall.

The section height is not noted on the sidewall of a tire but it is also measured in millimeters. The section height is approximately the distance from the rim to the tread surface of the tire when it is not carrying any weight.

TIRE TYPE

Some tires have a P or LT in front of the tire width, identifying them for passenger or light truck use.

Tires with a “P” are for passenger car use. Some passenger car tires may not have a “P” and are considered hard-metric tires. Some light trucks and SUV’s are equipped with original equipment P-metric or hard-metric tires. Tires with a “LT” are for light truck or SUV use only.

TREADWEAR, TRACTION,
AND TEMPERATURE GRADES

The UTQG code provides consumers with information on tire treadwear, traction, and operating temperature resistance.

Uniform Tire Quality Grading

The Uniform Tire Quality Grading System, or UTQG, is a system developed by the government designed to provide consumers with information on tire treadwear, traction, and operating temperature resistance. A number, followed by two to three letters, identifies the grade on the sidewall.

Treadwear Rating

The treadwear grade is a comparative numerical rating based on the wear rate of the tire when tested under controlled conditions on a specified government test course. For example, a tire graded 200 would wear twice as well on the course as a tire graded 100. The rating increases in 20-point increments. It is important to note that the true performance of a tire depends upon the actual conditions of its use. Actual conditions may depart significantly from the test conditions due to variations in driving habits, service practices and differences in road characteristics and climates.

Traction Rating

The traction rating indicates the tire's ability to stop a vehicle moving straight forward on wet pavement. The ratings are AA, A, B, and C, with AA being the best.

Temperature Rating

The temperature rating indicates the tire's ability to effectively dissipate heat. The ratings range from A to C, with A being the best.

DOT TIRE IDENTIFICATION NUMBER

The DOT tire identification number indicates compliance with all safety standards established by the U.S. Department of Transportation and provides additional information about the tire.

The DOT tire identification number indicates compliance with all safety standards established by the U.S. Department of Transportation and provides additional information about the tire manufacturer.

Located on the sidewall of a tire, the complete DOT tire identification number is a combination of up to 12 numbers and letters that provide valuable information.  The first two are the plant code where the tire was manufactured, and the last three to four numbers represent the week and year the tire was built.

The last four digits in this example, 1309, mean this tire was manufactured in the 13th week of 2009.

On the sidewall opposite the complete DOT number, is a partial DOT tire identification number.  With manufacturer, plant and tire size information, the partial DOT number helps you identify the tire when the full DOT number is mounted towards the inboard side of the vehicle and consequently not visible unless the vehicle is put on a lift for inspection.  

This is the partial DOT number for the full DOT number show above.
 


Prior to 2000, tires had just three numbers to represent the week and year of production.  In the 1990’s they added a triangle to identify the decade.


The last three digits, 517, plus the triangle in the example above mean this tire was manufactured in the 51st week of 1997. In the absence of the decade triangle, this tire would have been made during the 51st week of 1987.

For assistance in reading your DOT tire identification number, please contact us.

MOUNTAIN

 
M+S designates a mud and snow tire.

A tire with M+S (or a variation thereof) on the sidewall has met the Rubber Manufacturers Association (RMA) guidelines for a mud and snow tire.  These tires have been designed to provide better starting, stopping, and driving performance in snow conditions than non-M&S tires

SNOW

 
The mountain/snowflake designate a tire designed for severe snow conditions.

The mountain/snowflake located next to M+S (or a variation thereof) designates a tire designed for severe snow conditions. To receive this mark, tires must meet the testing guidelines established by the RMA in their Definition for Passenger and Light Truck Tires for use in Severe Snow Conditions.

 
 

LOAD INDEX & SPEED SYMBOL

The load index number and speed symbol correspond to the maximum load-carrying capacity of the tire and its maximum speed capability.

The load index is an assigned number that corresponds with the load-carrying capacity of the tire. For example, "96" indicates a load-carrying capacity of 1565 lb at maximum inflation pressure. The load index for most passenger car tires ranges from 75-100.  Click here to view the complete load inflation index.

Load Index Chart

Load index chart

Speed ratings are determined by indoor laboratory testing methods, which measure high-speed tire durability under controlled test conditions. These test procedures do not take into account underinflation, tire damage, vehicle characteristics or road conditions which can lead to sudden tire failure or loss of vehicle control at much lower speeds than indicated by the tire's speed rating.

Speed Symbol Chart

speed symbol chart

When replacing tires on your vehicle, you should use replacement tires with a speed rating equal to or greater than that of the original equipment tires if the speed capability and handling characteristics of the vehicle are to be maintained.

Remember to never operate your vehicle in an unsafe or unlawful manner. Your Toyo Tires dealer can provide you with more information on speed ratings.

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DIAMETER

Diameter The diameter indicates the size of the wheel from one side to the other.. You can learn more about changing the diameter of the wheels of your car in the Plus Sizing section.

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RADIAL

The "R" stands for "radial," indicating the tire has radial construction.

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ASPECT RATIO

Aspect Ratio The aspect ratio is the dimensional relationship of the section height to the section width. The lower the aspect ratio, the shorter the sidewall and the wider the shoulder-to-shoulder width.

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WIDTH

Width 

The width of a tire is referred to as its section width.  The width indicates the widest point of a tire from sidwall to sidewall.

The section height is not noted on the sidewall of a tire but it is also measured in millimeters. The section height is approximately the distance from the rim to the tread surface of the tire when it is not carrying any weight.

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TIRE TYPE

Tires with a “P” are for passenger car use. Some passenger car tires may not have a “P” and are considered hard-metric tires. Some light trucks and SUV’s are equipped with original equipment P-metric or hard-metric tires. Tires with a “LT” are for light truck or SUV use only.

Back to top

TREADWEAR, TRACTION, AND TEMPERATURE GRADES

Uniform Tire Quality Grading

The Uniform Tire Quality Grading System, or UTQG, is a system developed by the government designed to provide consumers with information on tire treadwear, traction, and operating temperature resistance. A number, followed by two to three letters, identifies the grade on the sidewall.

Treadwear Rating

The treadwear grade is a comparative numerical rating based on the wear rate of the tire when tested under controlled conditions on a specified government test course. For example, a tire graded 200 would wear twice as well on the course as a tire graded 100. The rating increases in 20-point increments. It is important to note that the true performance of a tire depends upon the actual conditions of its use. Actual conditions may depart significantly from the test conditions due to variations in driving habits, service practices and differences in road characteristics and climates.

Traction Rating

The traction rating indicates the tire's ability to stop a vehicle moving straight forward on wet pavement. The ratings are AA, A, B, and C, with AA being the best.

Temperature Rating

The temperature rating indicates the tire's ability to effectively dissipate heat. The ratings range from A to C, with A being the best.

Back to top

DOT TIRE IDENTIFICATION NUMBER

The DOT tire identification number indicates compliance with all safety standards established by the U.S. Department of Transportation and provides additional information about the tire manufacturer.

Located on the sidewall of a tire, the complete DOT tire identification number is a combination of up to 12 numbers and letters that provide valuable information.  The first two are the plant code where the tire was manufactured, and the last three to four numbers represent the week and year the tire was built.

The last four digits in this example, 1309, mean this tire was manufactured in the 13th week of 2009.

On the sidewall opposite the complete DOT number, is a partial DOT tire identification number.  With manufacturer, plant and tire size information, the partial DOT number helps you identify the tire when the full DOT number is mounted towards the inboard side of the vehicle and consequently not visible unless the vehicle is put on a lift for inspection.  

This is the partial DOT number for the full DOT number show above.
 


Prior to 2000, tires had just three numbers to represent the week and year of production.  In the 1990’s they added a triangle to identify the decade.


The last three digits, 517, plus the triangle in the example above mean this tire was manufactured in the 51st week of 1997. In the absence of the decade triangle, this tire would have been made during the 51st week of 1987.

For assistance in reading your DOT tire identification number, please contact us.

Back to top