Interpreting Tire Ratings

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Your tires may seem like pretty basic round pieces of rubber, but they are so much more than that. Within that black material lies steel reinforcements and all types of polymers and other components that influence everything from how well the tire holds air to the maximum temperatures the tire can withstand.

You don’t have to consult a lengthy manual to get the 411 on your tires. You can actually find all that information marked right on the side of the tire.

You don’t see anything on your tire that says, “Not to exceed 2000 pounds?” That’s because you won’t see the information spelled out in text. Instead, you’ll find a series of numbers of letters on the sidewall of your tire that will give you all that information.

Understanding how to read these marks will help you make the best selection when you shop tire stores in Cincinnati. Even if you don’t, the sales associates at McCluskey Chevrolet, one of the best tire stores Cincinnati has to offer, will walk you through the ratings and give you all the information you need.

Here’s your primer to reading those markings:

Tire Class

The first letter you will see in the code on the sidewall refers to the class of the tire. “P” stands for passenger, “LT” stands for light truck, “ST” stands for special trailer” and “T” stands for temporary, such as a doughnut.

Tire Width

A series of numbers will start right after that first letter (or two), and the first two to three numbers refers to the width of the tire. The measurement is separated from the next series of numbers by a slash.

The number refers to the width in millimeters. Therefore, if you see 215, that means your tires are 215 millimeters wide.

Aspect Ratio

Aspect ratio refers to the comparison between the tire height and width. Aspect ratio is indicated by the two numbers following the width.

The lower the number, the better the performance of the tire, generally speaking. A lower sidewall in relation to the width of the tire will provide better steering response.

Tire Construction

After the aspect ratio, you will see a letter in the code. This letter represents the class of tire construction. An “R” represents radial construction, while a “B” represents bias-ply tires.

Radial construction is now the industry standard for passenger cars, so you will likely always see an R rating. Bias-ply tires are used for some trucks, so you may still see this rating on some commercial trucks.

Rim Diameter

The numbers begin again after the construction rating. These next numbers refer to the diameter of the wheel, or rim. You must purchase tires that match the diameter of your rim to get a proper fit and ensure safe handling.

If you want to upgrade the size of your tires, you may also need to upgrade the wheels.

Load Index

A space follows the rim diameter, and the next numbers refer to the load index. This number tells you how much weight the tire can handle. However, the number does not translate directly to pounds. Therefore, if you see a 95, that doesn’t mean the tire can handle only 95 pounds. Instead, you have to look up a load-carrying capacity chart like this one (http://www.discounttire.com/dtcs/infoLoadIndex.do) to determine the weight. A 95 indicates that a tire can bear 1,521 pounds.

The load index shows what each tire can bear individually. To understand the full capacity of your vehicle, you will have to add up the capacity of each tire.

For passenger vehicles, tire capacity is not often an issue. However, it is very important to pay attention to load index when shopping for truck tires since trucks are built for hauling heavier loads. You will also need to know how much weight the truck is designed to carry since the suspension can only handle so much weight.

Speed Rating

Right next to the load index is a number that refers to the tire’s speed rating. There are 22 possibilities, and the letters range from B to Z. For example, a tire rated V can handle speeds up to 149 mph.

Tires will not immediately fail if they exceed their speed rating. However, running these tires at excessive speeds for extended periods can cause failure.

DOT Code

Every tire should also be stamped with the letters “DOT,” which indicates that it has met the minimum safety standards established by the U.S. Department of Transportation.

Behind the letters is a code that is used to track your tire. If a recall is issued, the code is used to contact owners to let them know.

At the end of the code are four letters that indicate the date the tire was manufactured. The first two letters refer to the week, and the last two letters refer to the year. Therefore, 2015 would indicate that a tire was made in the 20th week of 2015.

Older tires have only three digits for the date. The last number indicates the year of the decade. Therefore, a “7” means that the tire was produced in the seventh year of the decade. The flaw in this system is that you don’t know which decade.

Traction Rating

Somewhere on your tire, you should also see a traction rating. You can identify it by the word “traction” followed by a letter — AA, A, B or C. The rating is a measurement of how well the tire performed in braking and water tests. The best rating is AA, and the worst is C.

Temperature Rating

Also somewhere on the tire is a temperature rating with the word “temperature” followed by the letter A, B or C. A rating of A indicates that the tire can withstand the highest heats at high speeds. These tires are meant for performance vehicles, such as those that can reach high speeds.

Treadwear Rating

The word “treadwear” followed by a number should also appear somewhere on your tire’s sidewall. The rating should be read in comparison to the industry standard for tread durability, which is 100. Therefore, a tire with a treadwear rating of 120 is slightly more durable than the industry standard, while a tire with a 200 rating is twice as durable.

Understanding these ratings can help you choose the best tires for your vehicle, your budget and your desired performance. Visit one of the best tire stores Cincinnati has to offer, McCluskey Chevrolet, to find the best tires for your vehicle. Our sales associates will walk you through these ratings to help you make the best selection.