Tire speed ratings are a designation indicating the tires designed speed capability. They are the maximum speed that a tire can safely carry a load for a sustained amount of time in ideal conditions. The speed rating system was developed to help control the safe performance of tires at standardized speeds. The ratings are given 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 you’ll have at higher speeds. However, 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.

Tire speed ratings are usually found in the owner’s manual, driver’s side doorjamb, glove box door, and gas tank hatch. They are also easy to locate on the tires sidewall, usually the last item in the character sequence in the tire’s size code. For example, in the tire code “P205/60R16 82S,” S is the speed rating. It is important to ensure that the speed rating on each tire matches what the manufacturer recommends.

Tire speed ratings are based on laboratory testing with simulated speeds and loads. To receive any kind of rating, a tire must demonstrate that it’s capable of sustaining a particular speed. The rating system shows the top speed for which a tire is certified, but it does not indicate the total performance capability of a tire.

In summary, tire speed ratings indicate the maximum speed that a tire can safely carry a load for a sustained amount of time in ideal conditions. They are given a letter from A to Z, ranging from 5km/h (3mph) to above 300 km/h (186 mph). It is important to ensure that the speed rating on each tire matches what the manufacturer recommends.