How to read a tire’s sidewall:
Load Index & Speed Symbols
The load index is an assigned number that corresponds with the load-carrying capacity of the tire.
Speed ratings are determined by indoor laboratory testing methods which measure high speed tire durability under controlled test conditions. When replacing tires on your vehicle, use replacement tires with a load index and speed rating equal to or greater than that of the original equipment tires in order to maintain speed capability and handling characteristics.
 UTQG Ratings
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 range.
The UTQG Treadwear Rating is a comparative numerical rating based on the wear rate of the tire when tested. For example, a tire graded 150 would wear 1 1/2 times as well on the course as a tire graded 100.
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.
Letter Designations on Tires
“P” stands for “passenger” tire. “R” stands for “radial,” indicating the tire has radial construction. “LT” stands for “light truck.” “M+S” indicates the tire is designed for mud and snow applications, and all season applications.
U.S. DOT
The letters “DOT” certify compliance with all applicable safety standards established by the Department of Transportation (DOT). Beside this is a tire identification or serial number.
Proper Inflation
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.
You will find the recommended pressure on a placard or sticker in the door jamb, glove compartment, or near the gas cap. The tire placard tells you the maximum vehicle load, the cold tire pressure, and the tire size recommended by the vehicle manufacturer.
Check inflation pressure (including the spare) at least once a month and before every long trip. Tires must be checked when cold (before they have run a mile). Underinflation or overloading creates excessive heat, and can lead to tire failure, which could result in vehicle damage and/or serious injury or death.
Balance
You may have noticed the small weights placed on the rim of your tire. These weights help the tire remain balanced at all speeds. At high speeds a tire which is not balanced properly can generate severe vibrations. An unbalanced tire and wheel can also lead to irregular treadwear.
Some expensive alloy wheels can be damaged with the use of standard lead weights and may require the use of a coated weight.
Rotation
The purpose of regularly rotating tires is to achieve more uniform wear for all tires on a vehicle. Before rotating your tires, always refer to your individual owner’s manual for rotation recommendations. If no rotation period or pattern is specified, consider rotating your tires, front to back, every 6000 miles or at least every 7500 miles. Irregular wear may require more frequent rotation. Load Index & Speed Symbol Diameter Radial Aspect Ratio Width Passenger Car Tire U.S. DOT Serial Number Treadwear, Traction & Temperature Grades Maximum Cold Inflation Maximum Load Limit |
