View Here : Tire Rating Chart
The tire speed rating is the maximum speed tires can safely carry a load (the original weight of your vehicle plus whatever's in it) for a sustained amount of time in ideal conditions. The rating is molded on the tire sidewall , signified by a letter or two, usually after the load index number.
Tire Construction. After the speed rating is the tire construction, which has two options: Belted (B) or Radial (R). “Belted” means fiberglass, Kevlar or aramid fiber belts, which has added strength and load capacity.