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.
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 two times as well on the course as a tire graded 100. The relative performance of a tire depends upon the actual conditions of its use which may depart significantly from the test conditions due to variations in driving habits, service practices, and differences in road characteristics and climates.
The UTQG 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.
The UTQG Temperature Rating indicates the tire's ability to effectively dissipate heat. The ratings range from A to C, with A being the best.
*(UTQG treadwear goes in 20 point increments)
With the right amount of air pressure, your tires will perform better, wear longer and save fuel. The "right amount" of air pressure for the original equipment or same size tires is specified by the vehicle manufacturer and may be different for front and rear tires.
U.S. Dot Standard Safety Code
The letters "DOT" certify compliance with all safety standards established by the U.S. Department of Transportation (DOT). This is followed by a combination of up to 12 numbers and letters.
The first two numbers or letters 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.
Tires built in the 1990's will have three numbers and may have a triangle to note the decade. Examples are below.
Note: Recently it became mandatory to apply a partial DOT serial number on the sidewall opposite the complete DOT serial number. The partial DOT serial does not show the week and year that the tire was manufactured, but may still assist consumers in identifying tires should a recall be necessary. The purpose in applying the partial DOT serial number was to facilitate tire identification when the full DOT serial number may have been mounted towards the inboard side of the vehicle, and consequently not visible unless the vehicle was put on a lift for inspection.
Tire Size, Load Index, and Speed Symbol
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.
The width of a tire is referred to as its section width. This is the width of an inflated tire in millimeters at its widest point from sidewall to sidewall.
The section height of the tire is measured in millimeters also. The section height is approximately the distance from the rim to the tread surface of the tire when it is not carrying any weight.
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.
The "R" stands for "radial," indicating the tire has radial construction.
This One is Easy!
The "20" indicates the diameter of the wheel in inches. You can learn more about changing the diameter of the wheels of your car in the Plus Sizing section.
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.
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.