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Tire speed ratings: why it’s important to comply with them

Published on June 16, 2023

2 mins reading time

What is a tire’s speed rating? It’s a code that tells you the maximum speed at which a tire can sustain the vehicle load it is designed to support. When the time comes to replace your vehicle’s original tires, be sure to comply with their speed rating. With today’s suspensions, car manufacturers attach more and more importance to this rating.

Buy tires with the right rating

A vehicle originally delivered with tires rated H or V will offer not perform as well with S-rated tires installed (see the chart below). Steering, braking, handling and stability can all be affected, because the sidewalls of an S-rated tire are not as stiff as those of an H- or a V-rated tire.

What about winter tires?

You can install winter tires with a lower speed rating than that of your vehicle’s regular tires. You should stick as close as possible to the original rating, though, because your car’s onboard computer is calibrated to “feel” the road through tires with that rating. A different speed rating could send the wrong data to the computer, resulting in various issues.

How to read the information on a tire

The speed rating is always indicated on the tire itself, right after the size information. Here is a key to the information on a tire branded P205/65R15 92H:

Letter P: indicates the tire is designed for use on a passenger car
Number 205: width of the tire in millimetres
Number 65: ratio of the height of the sidewall to the width of the tire
Letter R: means it is a radial tire
Number 15: diameter of the wheel in inches
Number 92: this is the tire’s load index, representing the maximum load that it can carry when properly inflated (in this case, 630kg)
Letter H: this is the speed rating (in this case, 210km/h).

To find out the speed rating to be complied with when purchasing tires for your vehicle, see the owner’s manual. And don’t hesitate to contact your garage mechanic or CAA-Quebec Mobility Advisory Services for more information. 