Tires 101: How to Read a Tire Sidewall

American Tire Distributors (ATD) is one of the largest independent suppliers of tires to the replacement tire market. We operate more than 140 distribution centers, including 25 distribution centers in Canada, serving approximately 80,000 customers across the U.S. and Canada. With more than 80 years of experience, we know a thing or two about tires and we want you to be safe every time you get behind the wheel.

Do you know what the markings on the side of your tires are? When trying to read a tire, it can be similar to that of a foreign language. We’re here to help make you fluent in tires. We will be covering a P-Metric tire, as they are the most common, however roughly 5% of the vehicles on the road have other types (ex. Metric/Euro-Metric).

1. Type: The letter listed before the set of numbers. Depending on your vehicle, this is typically either P for Passenger or LT for Light Truck. A spare tire will have a T indicating Temporary, while a trailer tire will be labeled ST for Special Trailer.

2. Section Width: The section width is the width of the tire from one sidewall to the other measured in millimeters. In this example, the tire is 205 millimeters wide.

3. Aspect Ratio: The aspect ratio refers to the height of the sidewall. It’s a percentage of the section width. In this example, the sidewall height is 65% of the 205 section width which equals 133.25 millimeters.

4. Construction & Wheel Diameter: The letter R stands for Radial, the type of tire that fits the vehicle. The number is the diameter of the tires inner rim. In this example, the tire will fit a 16-inch wheel.

5. Load Index: The load index is the tire size’s assigned numerical value used to compare load carrying capacities. In this example, the 99 identifies the tires ability to carry approximately 1,201 pounds.

6. Speed Rating: The speed rating designates the maximum speed at which a tire can be driven. In this example, the speed rating is H, which means it can be driven at speeds up to 130 mph.

7. Ply Construction: This is an expression of the tire’s strength and capacity. The ply rating translates in a very direct way to tire capabilities and limitations, especially when it comes to inflation and load capacity. If you plan to haul, tow or carry heavy loads with your vehicle, we recommend familiarizing yourself with the ply rating of your tires.

8. DOT Identification Number: Register your tires with the DOT. When you purchase new tires, your installer should provide you with a DOT card so you can record the DOT numbers of your tires and send them to the manufacturer. This information is important, as it’ll be used to notify you in the event of a tire safety recall. If your installer doesn’t provide you with a DOT card, you may also be able to register online on the manufacturer’s website. Most manufacturers provide online registration for DOT numbers.

9. Misc. Items: You will also be able to locate the maximum permissible inflation pressure and the maximum load rating of the tire.

From your friends at ATD, we want you to be prepared for the road ahead so you can thrive and drive into the future. Follow along our Tires 101 blog as we explore the world of tires.

Who we are as people is who we are as a company. We share the same values in the way we work with each other, our partners and our customers. We are ATD.