How to Read a Tire Rating

Tires ratings are important for correct matching and vehicle safety.  All tires have ratings that can be found on the sidewall of the tires. Learning how to read the ratings and what they mean will aid in buying the correct tire for a vehicle.

• Read over the number on the sidewall, for example “P205/75R17.”


• Examine the number-letter combination. The first letter type of vehicle the tire was created for. T- is for a spare tire but not always found on a spare tire, LT- Light truck, C- commercial use, P- passenger.


• Find the next set of numbers next to the first letter. This will be a three-digit number then a forward slash (/). This number designates the width of the tire. The width is from the sidewall edge to sidewall edge. This is done in millimeters. The numbers range from small to larger designating the higher the number the wider the tire.


• Read the next number. The next number after the forward slash is a two-digit number. This number is the aspect ratio. The number describes the height of the sidewall as the percentage of a width of a tire. An example is 205/75. This means that a tire is 205 millimeters wide and the sidewall height is about 154 millimeters. This means 75% x 205. This is done with all tires.


• Find the next letter, which is just after the aspect-ratio number. The letter is R. This means radio construction, which has been how tires have been constructed for many years. The other letters that may be seen are B- bias belted or D- diagonal bias.


• Read the last number. This indicates the size of the rim the tire is able to fit into. The wheel sizes are 13,14,15 or 16 with some larger sizes available. This number is measured in inches and tells the diameter of the wheel.


• Check to see if there is more information after the tire size number. There may be about two more ratings. This will be a number and letter. The number is the load index, which is the maximum weight that the tire can handle. The letter designates the speed index for the tire. This is the highest speed the tire was designed to be able to handle. It is important to know that the letters are not done in order the same way the width of the tire is done.


• Look for the Uniform Tire Quality Grading. This will only be found on passenger car tires. Treadwear which is how long the tread will last. Then the traction rating which is done using AA, A, B, C with AA being the best. Temperature explains how the tires resistance to heat is. This is done using A, B, C with A being the highest rating.


• Choose the proper tire that matches the current tire measurements. This will ensure proper fit and performance.