How Are Tires Rated?

Trying to understand the rating system for tires is not very easy. If you don’t know much about tires in general, it’s downright confusing. But, when it’s time for a tire change, you should know as much as possible about the tire rating system so that you buy the best new tires possible.

So, what do tire ratings mean? What are the ratings of a good tire? What should a consumer be looking for? Before getting into all those details, first, we need to understand the origins of tire ratings.

The Basics of Tire Ratings

Every company that sells tires has to ensure that their product complies with certain guidelines and standards that governmental bodies have set. Specifically, they have to abide by the Federal Motor Vehicle Safety Standard 109. They also have to comply with different standards that the tire industry has established as a whole. The numbers and letters that are found on the side of a tire are a very important part of knowing the factors that go into a tire’s rating and what exactly it all means for the tire and the consumer. The numbers on the side of the tire correspond to different factors like temperature, speed, load, traction, and tread-life.

It’s important for consumers to remember that compliance with any government or industry standards is done with no government oversight. A lot of industry officials say that the periodic audits of tire production by government officials have not been conducted in a long time. However, the companies are supposed to still follow the standards, even on the lowest quality tires. Just be sure to keep all this in mind the next time you are out buying a tire for a tire change.

Standard 109 Requirements

Before going any further, let’s go over the “Standard 109 Requirements”. These requirements are additional standard requirements for tires. All tires have to pass tests designed to determine temperature thresholds, traction and tread life of tires to see if they comply with Standard 109 guidelines. Additionally, all tires are rated for speed, load, and dimension. If all requirements are met and the tires hold up to the industry standards, then they are ready to hit the consumer market.

Temperature Ratings

Tire temperature ratings are designated with C, B, and A, with A being the rating that best indicates whether a tire has the ability to hold up against heat. High heat can very quickly ruin the structural integrity of a tire. A “C” rating will be given to a tire that can survive a test that has been conducted on tires since 1968. In this test, the tire is put onto a machine where a steel roller is run on it for two hours at 50 mph, half an hour at 75 mph, an hour at 80 mph, and then finally another half an hour at 85 mph.

A tire will achieve a “B” or “A” rating if the tire is tested in a similar manner but at higher speeds and for longer. The higher the tire’s rating, the better the tire will be at handling heavy loads for long periods of time on very hot days.

Speed Ratings

One might assume that the tire’s speed rating would be tested and rated the same way as temperature ratings, but it is not. The speed rating for tires is set up in four different basic categories of S, T, H, and Z. Although a few more categories exist in the rating system, they are not very common.

S is the lowest rating. For a tire with an S rating, a motorist should safely be able to drive as fast as 112 mph. A tire with a T rating will safely go as fast as 118 mph, a tire with an H rating will safely go as fast as 130 mph, and lastly, a Z tire will go as fast as 149 mph.

Load Ratings

The load rating in the tire rating system is rather hard to understand for most consumers. All tires are rated in accordance with the amount of weight that they can safely support. However, this rating is not based on the actual weight; instead, it is based on an index. For instance, a tire with a load rating of 92 corresponds to about 1,400 pounds. Essentially, when it comes to tire load ratings, the higher the rating is, the stronger the tire is. A consumer should ensure that the tire they are buying has a load rating that matches what the vehicle’s owner’s manual suggests.

Experts in the tire industry claim that there is no connection between the different ratings that the tire gets. They all vary from type to type of tire; it all comes down to the tire’s materials, design, and construction.

Traction Ratings

Another feature of tires that gets a rating is traction. Traction is what allows a tire to grip the road and move, or stop, the car accordingly. When it comes to traction, all tires are categorized with traction ratings of either “C”. “B”, “A”, or “AA”. What makes a tire eligible for the different ratings is based on guidelines set by a government-sanctioned skid test that is conducted on wet surfaces.

Tread-Wear Ratings

The tire tread-wear rating is meant to inform consumers how long they can expect the rubber tread on the tire to last. The test that determines the rating involves taking the tire out for a test drive for a pre-determined distance. Data is then taken from that test drive and then used to predict the overall life of the tread and the tire itself. The number is determined from a baseline of 100. So if a tire has a tread-wear of 200, it should last for about twice as long as a tire that has been rated with 100.



So, now that you know how tire ratings work, your next tire buying experience should go a lot smoother. If you see a model of tire for sale with a temperature rating of B, a speed rating of T, a load rating of 92, a traction rating of A, and a tread-wear rating of 100, you will know exactly what all of that means and if it is the type of tire you need. You can also now look at the tires you have now to determine if you require a tire change.