Tire Speed Rating Safety

The tire safety rating shows the maximum speed a tire can withstand. If you exceed the speed rating of the tire, you risk blowing out the tire.

Function

A letter of the alphabet represents the speed rating of the tire. For example, "Q" represents 99 mph, while "V" represents 149 mph. You should not exceed the maximum speed of the lowest-rated tire on your car.

Identification

You can find the tire rating of the car next to the load rating on the tire. The load rating is two numbers, so you need to find a group of three characters--two numbers followed by one letter.

Warning

The original speed rating of a tire applies only if the tire is properly inflated and is undamaged. If the tire has been cut or punctured, even if it was professionally repaired, you cannot count on it performing up to its rating.

Considerations

Tire speed ratings use kilometers per hour as the standard unit and are converted to miles per hour, so the ratings do not appear to have a clear pattern.

Potential Issue

Federal law does not require tire manufacturers to put a speed rating on tires, so your tire may not have the information on the sidewall. If your tire does not have the information, contact the tire manufacturer.

References

• Department of Transportation: Tire Safety
• Tire Rack: Tire Tech Information