Tire Speed Rating
What is tire speed rating?
A tire’s speed rating indicates the optimal speed that the tire can safely maintain over time. The higher the speed rating, the better control and handling you’ll have at higher speeds.
The speed rating system was developed to help control the safe performance of tires at standardized speeds. A tire’s certified speed rating is given a letter from A to Z, ranging from 5 km/h (3mph) to above 300 km/h (186 mph).
This rating system (see below) shows the top speed for which a tire is certified. It does not indicate the total performance capability of a tire.
Speeding through the years
When the speed rating system was developed, the "Unlimited V" category of over 210 km/h (130 mph) was the top speed rating possible.
As manufacturers developed bigger and better tires, it became necessary to regulate performance at standardized speeds to ensure safety. The "Limited V" category of 250 km/h (149 mph) was then created, and eventually the "Z" speed rating was added as the top speed rating. (Always consult the manufacturer for the maximum speed of Unlimited Z tires.)
More recently, standardization has changed so all ratings except "Unlimited ZR" incorporate the speed symbol and load index as part of every tire’s service description. For example:
|205 = Section Width in Millimeters|
|60 = Aspect Ration|
|R = Radial Construction|
|15 = Rim diameter in Inches|
|91 = Load Index||Service Description|
|V = Speed Symbol|
When "ZR" appears in the size designation with the service description, the maximum speed is indicated by the service description. For example:
|Tire Designation||Maximum Speed|
|P275/40ZR17 93W||270 km/h (168 mph)|
|P275/40ZR17 93Y||300 km/h (186 mph)|
Tire Speed Capabilities
For tires with a maximum speed capability higher than 240 km/h (149 mph), a "ZR" may appear in the size designation. Tires with a maximum speed capability higher than 300 km/h (186 mph), require a "ZR" in the size designation. Consult the tire manufacturer for maximum speed when there is no service description.
TIRE SPEED CAPABILITIES
|Symbol Speed||Speed (km/h)||Speed (mph)|