Motorcycle Tire Letter Ratings. P, lt, st, or t. The letter between the second and third numbers, either r or b will tell if you if the tire is bias ply or radial.
Motorcycle tire speed ratings this letter represents the maximum speed under recommended load capacity. The width codes below are for motorcycle tires with an aspect ratio of 80 or greater. The first two digits (87s) represent the tire's load index and are followed by a single letter (87s) identifying the tire's speed rating.
Please note that the values in this chart are the rim width not the tire width.
A second letter may follow the first, indicating type of construction: Can a motorcycle tire be repaired? See load index chart below. The first letter is the tire’s speed rating, and indicates the maximum speed for which the tire was designed.