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D.O.T. Markings

DOT marking serves as the tire’s fingerprint and signifies compliance with U.S. Department of Transportation Tire Safety Standards.

Example: DOT M5H3 459X 063

The first two characters M5 designate the tire’s manufacturer and plant code. The third and fourth characters denote the tire size. The fifth, sixth, seventh and eighth (optional) characters identify the brand as well as other significant characteristics. The final three numbers (four numbers, beginning in 2000) denote the date the tire was produced, with the first two indicating the week, and the last number indicating the year (063 indicates the tire was built in the 6th week of 2003).

How to Choose a Tire

  • Buy the right size tire. The appropriate tire size for your car can be found in the owner’s manual or on a placard located somewhere in your vehicle. Also, consider the car’s original equipment when purchasing a replacement tire
  • Consider factors such as load-carrying capacity of the tire, as well as traction, treadwear and temperature grades, also known as the Uniform Tire Quality Grade System
  • When tire shopping, keep in mind that there is a difference between the lowest price and the best value. As a consumer; finding the highest quality tire that will fulfillyour specificneeds at the most competitive price should be the ultimate goal
  • When purchasing a tire, be sure to fill out and mail the DOT tire registration card so you can be notified of any product updates

How to Read a Sidewall

  • The first number (205 in this example) is a three-digit number which refers to the overall width of the tire, in millimeters
  • The second number (55) refers to the aspect ratio, which is the relationship between the tire’s height and its width. In this example, the sidewall’s height is about 55% ofthe tire’s width
  • The letter following the aspect ratio is usually an “R,” standing for “radial”
  • The next number indicates the diameter of the wheel rim on which the tire will fit (16 inches, in this example).
  • The final number and letter represent the load index and speed rating. The load index is an assigned number ranging from 0 to 279 corresponding with the load carrying capacity of the tire-that is, how much weight it is certified to carry at maximum inflation pressure. The rating can be matched against a load index chart to determine corresponding maximum weights.
  • The speed rating is a letter which indicates the range of speeds at which a tire is certified to carry a load (see the speed symbols chart to determine your tire’s maximum speed). Each tire is assigned a rating from A (lowest) to Z (highest) with one notable exception: the “H” rating falls out of sequence between “U” and “V” and is used for tires certified for speeds up to 130 mph. The “Q” rating is the lowest, commonly used for passenger cars. A “V” rated tire is certified up to 240 km/h or 149 mph.

It’s important to note that markings do not always appear exactly as they do in this example, as tires can be certified under a variety of designations.

Tips For Proper Inflation

Purchase an accurate pressure gauge, as it’s impossible to tell how much air is in the tire by looking at it. The gauges attached to air hoses may not be accurate. It is normal for all tires to lose air over time.

The pressure should never be below the recommended pressure listed on the vehicle placard nor above the maximum branded on the sidewall of a specific tire in normal driving conditions.

Tire Safety and Maintenance

  • You should check each tire’s air pressure (including your spare) once a month and always before a long trip. Always check when they’re “cold” (that is, at least three hours after the vehicle has been stopped, or before it has been driven one mile)
  • Load carrying limits molded into the tire’s sidewall should never be exceeded. Consult an ACCCtrained tire professional to verify limits for the tire that you’ve chosen
  • If for some reason you cannot safely avoid a road hazard and you run over glass, rocks, curbs, or other foreign material, check the tire for external damage. If you suspect damage but can’t see it, have the tire demounted and checked for internal damage by a trained ACCCprofessional
  • The simplest way to check tread depth is to place a penny into the tread (Lincoln’s head first); if the top of his head remains visible, the tire needs to be replaced (lessthan 2/32″)
  • Tire rotation can be beneficial in several ways. When done at the recommended times, it can preserve balanced handling and traction of the tires and even out tire wear. It can even provide performance advantages
  • If you get stuck in mud or snow, don’t spin your tires to get out. Spinning, even for a few seconds, can build up heat and damage your tires
  • Properly balanced tires and wheels turn with all their weight distributed equally. Unbalanced tires can result in a vehicle’s “shimmying” (shaking from side to side) and “tramping” (hopping up and down)
  • Cleaning tires removes foreign substances that can degrade the tires from the tire surface. We recommend soap and water
  • If any tire sustains a puncture, have the tire inspected internally by any American Car Care Center for possible damage that may have occurred
  • Check your tires at least once a month for uneven wear and foreign objects wedged in the tread. A tire that continually needs more air should be taken off the vehicle and off the wheel and checked thoroughly

Uniform Tire Quality Grade (UTQG)

Each tire manufacturer is responsible for designating the rating of each of its tires. LT designated light truck tires do not have UTQG markings.

The Uniform Tire Quality Grade (UTQG) offers three more key pieces of information about a tire:

  • Treadwear grades – typically range from 60 to 620 in 20 point increments. The higher the grade, the longer the tread life.
  • Traction grades – indicate a tire’s braking performance. A grade from “AA” to “C” is assigned, with “AA” signifying the best traction.
  • Temperature grades – represent a tire’s ability to withstand heat under test conditions. Temperature grades are assigned “A” to “C,” with” A” signifying the most resistance to heat.
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