what is speed rating on tires

The speed rating on a tire is a measure of the tires designed speed capability, indicating the fastest speed a tire can handle before it no longer performs as designed. The speed rating is usually the last item in the character sequence in the tire's size code, and it is represented by a letter from A to Z, ranging from 5km/h (3mph) to above 300 km/h (186 mph) . The higher the speed rating, the better control and handling the tire will have at higher speeds. It is important to note that tire speed ratings do not imply that the vehicle may safely be driven at the maximum speed for which the tire is capable, particularly under adverse weather or road conditions. The speed rating can be found on the tire's sidewall, and it is usually listed alongside the load index. Vehicle manufacturers recommend a specific tire speed rating, which can be found in the manual or in other locations such as the driver's side door jamb, the gas tank hatch, or inside the glove box door.