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A Quick Guide to Reading a Tire Sidewall

Have you ever wondered what those numbers and letters on your tires mean? We’ll take you through the basics of the P-Metric Tire Code in our quick guide to reading a tire sidewall!

What the Numbers & Letters on a Tire Mean

Most of the vital information you need about your tires is printed on the sidewall. This code of letters and numbers makes up the P-Metric Tire Code.

Within this code, you can determine the tire class, section width, aspect ratio, tire construction, and rim diameter of the individual tire. In our quick guide to reading a tire sidewall, we’ll use the code “P 205/65 R 16” as an example and refer to it throughout.

Tire Class

The first thing your tire sidewall tells you is what tire class it belongs to, represented by the first letter. For most tires, this will be a P, which stands for a passenger-constructed tire.

It may also say LT or ST, which means the tire belongs to the light truck or special trailer-constructed tire class. If there’s no tire class letter, it’s likely because it was constructed in Europe or elsewhere that uses different standards than the US. Our example tire is a passenger-constructed tire class.

Section Width

Following the first letter is a three-digit number, which expresses the tire’s section width. This number identifies the tire’s width from sidewall to sidewall, represented in millimeters. In our example, the tire is 205 mm wide from sidewall to sidewall.

Aspect Ratio

Immediately following the section width is a backslash followed by a two-digit number representing the aspect ratio. This value is the sidewall height as a percentage of the section width.

Looking at our example of “205/65,” the aspect ratio is 65, meaning the sidewall height is 65 percent of its 205 mm section width, or approximately 133 mm.

Tire Construction

After the section width/aspect ratio numbers, another letter designates the tire’s construction type. Like the tire class, most tires have the same designation: an R.

The R stands for radial construction—the tire’s plies run at 90 degrees to the centerline of the thread. The other construction designation is a D, diagonal construction, but it’s rare on cars. Our example tire is a radial construction.

Wheel Diameter

Lastly, the wheel diameter is our final figure in the P-Metric Tire Code. As you might guess, the wheel diameter is the wheel size on which the tire can safely be mounted.

The wheel diameter is always represented as a two-digit number; while the section width is metric, the diameter is expressed in inches. In our example, the tire’s wheel diameter is 16 inches.

Tire have other markings and symbols, but the basic information of the P-Metric Tire Code found on the sidewall is what most drivers need to know. If you need to replace your tires in Clovis, you can shop for them online at RNR Tire Express. Just check the sidewall of your current tires to get the right ones!

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