A SIMPLE EXPLANATION OF 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. In short, it’s the fastest speed a tire can handle before it no longer performs as designed. 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 5km/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.
WHY WERE TIRE SPEED RATINGS DEVELOPED?
The speed rating system used today was developed in Europe in response to the need to control the safe performance of tires at standardized speeds. When the rating system was originally 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.)
WHERE CAN I FIND MY TIRE SPEED RATING?
You can find your tire speed rating in a number of places, typically in the owner’s manual, driver’s side doorjamb, glove box door, and gas tank hatch. Recent standardization has changed so all ratings except “Unlimited ZR” incorporate the speed symbol and load index as part of every tire’s service description on the tire’s sidewall. If you’re reading your tire sidewall, the speed rating will be the last item in the character sequence in the tire’s size code. Below is an example of a the description on a tire’s sidewall: 2015/60R15 91V. Here, the tire would have a speed rating of V. V-rated tires can be driven at 149 MPH.
|205 = Section Width in Millimeters|
|60 = Aspect Ration|
|R = Radial Construction|
|15 = Rim diameter in Inches|
|91 = Load Index||Service Description|
|V = Speed Symbol|
Tires having a maximum speed capability over 149 MPH may have “ZR” in the size designation. Tires with a maximum speed capability over 186 MPH are required to include “ZR” in the designation. Below are examples of tire sizes with a “ZR” speed rating.
|Tire Designation||Maximum Speed|
|P275/40ZR17 93W||270 km/h (168 mph)|
|P275/40ZR17 93Y||300 km/h (186 mph)|
TIRE SPEED RATING CHART
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)|