What Is a Tire Speed Rating?

Are you looking to buy tires for your vehicle? You have a wide range of choices to consider, as there are many different types of tires on the market.

Some of the differences between various tires can be glaringly obvious. For example, you’re not likely to confuse a tire made for city driving with a rugged, knobby tire designed for off-road use. However, there are other differences that can be less obvious to many drivers. One such difference involves tire speed rating. Understanding what this metric is and the role that it plays is important to choosing the right tire for your vehicle and your lifestyle, as tire speed rating can have implications that affect vehicle safety.

Tire Speed Rating 101

Your tires keep your car connected to the road and provide the traction you need to maintain control of the vehicle. Tires are designed to deliver optimal performance within certain speed limits, and once a certain speed is exceeded, the tire’s performance usually begins to diminish.

A tire’s speed rating indicates the fastest speed that it can handle before its performance begins to suffer. If you exceed a tire’s speed rating, you may experience diminished traction, which can make it more difficult to maintain control of the vehicle and may create conditions that increase the likelihood of an accident.

A tire’s speed rating isn’t the only factor to consider in deciding how fast you want to drive. Of course, the speed limit is perhaps the most relevant factor in play, but you should also consider that tire condition, tire pressure, terrain and weather may affect the speed at which you can safely travel.

How Is Tire Speed Rating Measured?

Tires are rated using designations of one or two characters. Each designation indicates the top speed at which the tire can safely travel, and the first character is always a letter of the alphabet.

At the bottom end is the A1 designation, which indicates a maximum speed of 3 mph. At the other end of the spectrum is the Y designation, which indicates a speed capability of up to 186 mph. Two of the most common speed ratings are S (112 mph) and T (118 mph), which are common among personal use sedans and vans. In some cases, a tire’s size information will include the letters ZR. This indicates that the tire is capable of traveling at speeds exceeding 186 mph.

Where Is the Tire’s Speed Rating Located?

If you want to find your tire’s speed rating, there are a few places you can look. The rating can often be found in the owners manual or on the glove box door. It may also be listed on the hatch of your car’s gas tank or on the driver-side door jamb.

Finally, you can check your tire’s sidewall to find its speed rating. The rating is typically the very last item in a sequence of characters that indicates your tire’s size code.

Here’s an example that should help to put it all together. Let’s say you check your tire’s sidewall and see the following sequence:

2015/60R15 91H

The tire speed rating is represented by H, the final character in the sequence.

Since a tire’s speed rating can affect vehicle performance and safety, it’s important to choose the right one for your vehicle in particular. Even if you’re not in the market for new tires anytime soon, it’s a good idea to check your vehicle’s current tires so you have a better understanding of the speeds at which you can drive safely.

Check out all the tire gauges available on NAPA Online, or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on tire speed rating, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Unsplash.