On the side of every tire is an alphanumeric system that describes the tire and its performance characteristics. The typical tire size system will appear as a string of letters and numbers such as: P215/70R16 100S
The first letter in the tire size indicates the type of tire and intended use. In this example, the first letter is 'P'? indicates the tire is a metric size used primarily on passenger vehicles. Other letter designations include T (Temporary Spare), LT (Light Truck Metric), C (Commercial), and ST (Special Trailer Service).