ALT-3 What the Numbers on your Tire mean
Selecting a tire isn't as simplistic as it seems. There are quite a few different variables that need to be considered when purchasing a car. The first thing that you need to know about tires however, is what each of the different numbers and letters on your tires mean. By knowing this information, you will be better able to understand what type of tires you are purchasing and how to pick ones that will better fit your driving needs.
Tire TypeThere are several different tire types. Depending upon the type of vehicle you have will determine what type you need. For example, if you have a passenger vehicle, you will have a 'P' tire type. If you are driving a smaller truck, you'll have an "LT" designation. If the tire is a donut or temporary tire, you'll see "T"
Tire WidthThe three digit number is the width of the tire in millimeters (mm), which is measured from one sidewall of the tire to the other. This measurement is done while it is on the selected rim, as the rim itself can affect the overall outcome of this measurement.
Aspect RatioThis number tells you the height of the tire, from the bead to the top of the tread. This is described as a percentage of the tire width.
Two tires with different aspect ratios but the same overall diameterHigh performance tires usually have a lower aspect ratio than other tires. This is because tires with a lower aspect ratio provide better lateral stability. When a car goes around a turn lateral forces are generated and the tire must resist these forces. Tires with a lower profile have shorter, stiffer sidewalls so they resist cornering forces better.
Tire ConstructionGenerally within the tire you are going to see R, B, or D for the tire construction. This essentially tells what type of construction was used in order to make the tire. The "R" is for radial, which is the most common type of tire and is used on most newer vehicles. Older vehicles sometimes will still have the "D" or Diagonal Belted or "B" Bias Belted constructure.
Rim DiameterThis number specifies the size rim that the particular tire was meant for. This is going to be measured in inches.
Uniform Tire Quality GradingPassenger vehicles are required to have tires that have been rated by UTQG. This is essentially a standard that tire manufacturers use to represent the variety of qualities of their tires. This helps consumers to better purchase the tires that are going to have the most benefit for their vehicle. This rating is broken into a few categories:
Tread Wear: The higher the number, the longer you can expect the tread to last. This is a good thing to know when purchasing cheaper tires. Generally they are cheaper but aren't going to last anywhere near as long as the more expensive ones. Many times you will find it is just cheaper to upgrade a bit.
Traction: Tire traction is rated as AA, A, B, and C. AA are the best tires and C are the worst. This is essentially the ability of the tire to stop on a wet surface. This of course is extremely important if you live in wet or icy areas where braking quickly could save you from an accident.
Temperature: This is the rating of how well the tire handles increased heat. The heat could be caused from long usage of your vehicle, warm temperatures or a number of other causes. The ratings are A, B, or C with A being the best and C being the worst. Generally tires are broken down even further as high A, low A, and so on. This is to show a tire's superiority at handling heat within each category.
Load Ratings: This is the amount of weight a tire can support. This is important to know especially if you are buying tires for a truck. If you don't get the correct tire to support the weight of your vehicle, your tire could blow out causing a serious accident.
Speed Rating: This number reflects the speed that you can put on each of the tires. If you drive at much higher speeds on a regular basis, make sure that you are purchasing a higher speed rating tire.
