Tire size dimensions are a series of letters and numbers on the sidewall of tires that indicate the tire size, type of tire and the performance rating. The dimensions and rating are important to know in order to ensure the correct tires are being used on a vehicle.
Tire size dimensions usually begin with a letter to signify the type of vehicle the tire is intended for. For example, a P225/50/R15 would be intended for a passenger car, whereas a T at the beginning would indicate that it is a temporary or spare tire. The numbers that follow are the tire width measured in millimeters. The next number grouping is the sidewall ratio to the tire width. The final number is the tire's inner construction type and diameter of the wheel in inches.