How to Read a Tire
There is a great deal of information on the sidewall of a tire besides the manufacturer and model; specifically about the tire's intended purpose, dimensions, internal construction, load index and speed rating. Using the example P 215/65 R15 89H M+S .
Most tire sizes begin with a letter or letters that identify the type of vehicle and/or type of service for which they were designed. In our example the letter P indicates the tire is intended for vehicles used as passenger vehicles.
- Temporary Spare
- Light Truck
- Special Trailer
Following the letter(s) that identifies the type of vehicle and/or type of service for which the tire was designed, the three-digit numeric portion identifies the tire's "Section Width" (cross section) in millimeters. In our example the number 215 tells us the tire is 215 millimetres across the widest point.
Sidewall Aspect Ratio
Typically following the three digits identifying the tire's Section Width in millimetres is a two-digit number that identifies the tire's profile or aspect ratio. This ratio compares the width of the tire to the tires sidewall height. In our example the number 65 indicates that this tire size's sidewall height (from rim to tread) is 65% of its section width therefore the tire in our example has a sidewall height of 139 mm.
Following the numbers indicating the Aspect Ratio is a letter that identifies the tire's internal construction. In our example the R indicates a Radial construction in which the tire's body (or plies) "radiate" out from the imaginary centre of the wheel. Radial tires are by far the most popular type of tire today representing over 98% of all tires sold.
- Radial bias
- Belted bias, which are not used in today's market
- Diagonal bias
- May be added to the Internal Construction indicator (such as RF) to indicate a self-supporting tire or "run-flat" construction.
Tire and Wheel Diameter
Following the construction designation, a number will indicate the diameter of the wheel the tire is designed to fit expressed in inches. In our example the number 15 indicates a 15-inch rim. Typical rim diameters range through 8, 10, 12, 13, 14, 15, 16, 18, 19, 20, 22, 23, 24, 26, and 28.
The next 3-character code represents the tire's service description. A service description identifies the tire's load index and speed rating. In our example the number 89 indicated the tire's load carrying capacity of 1,279 pounds. The letter H indicates the tire's top speed rating is 130 mph ( 210 k/hr. ). This is the maximum permitted speed that the tire can sustain for a ten-minute endurance without being in danger. There are detailed charts and tables that set out the load index and speed rating.
In our example, "M+S", (Mud and Snow), indicates an all-season tire. The snowflake and mountain symbol on the side of a tire indicates that it meets or exceeds the new snow tire designation specifications, and will provide you with optimum traction in severe snow conditions.
There are other codes imprinted on the sidewall of the tire, including the following:
All tires sold in Canada must have the "DOT" (Department of Transportation), or tire identification number, moulded into the sidewall. The first two characters after DOT indicate the manufacturer; the second two characters indicate the plant where the tire was manufactured.
This number gives the maximum cold pressure required to carry the maximum load for which the tire is rated. The maximum pressure number is not the same as the recommended tire pressure for your vehicle.
Important: Never exceed the maximum pressure written on your tire's sidewall. Explosive failure may occur as a result, leading to serious injury or death.
This number tells you the maximum amount of weight the tire can support when cold. Cold means the tire has been driven less than 2 km, or has been standing still for at least three hours.
The Excel Tire Way
Excel Tire Dealers are experts in tires. They will help you understand the characteristics of each tire and select the tire best suited to your driving needs.