The Service Description on a tire generally follows the Tire Size Code. It typically consists of a 2-digit number and a letter.
The 2-digit number referred to as the Load Index is code associated with the maximum weight the tire can carry. This number ranges from 71-98
The letter defines the Speed Rating of the tire. This indicates the maximum speed the tires can sustain for a 10 minute endurance during testing. Below are some of the more common ratings.