How Do I Figure Out the Size of My Tires?

Most of the time, when you are shopping for new tires, the service advisory you are speaking to can pull up your information and easily tell you the size of the tires on your car. Unless you are an enthusiast or buy your tires online, you probably haven’t given tire size much thought. That being said, you may run into a situation, like getting a flat, where you need to know your tire size. Finding this information is easy as long as you know where to look and what to look for. In this guide, we are going to tell you how to figure out the size of your tires quickly and easily when they are on your car!

Where Can I Find My Tire Size?

Sizing information is found on the sidewall of your tire. It will be presented as a series of numbers and letters, typically presented in the following format: P235/45R 17. You may see another number and letter combination after this, which represents the tire speed and load rating that we cover in a separate article.

How Do I Read Tire Sizing?

Providing this number to a professional will be all the information they need to find the right tires for your car. You don’t need to know what each number means, but if you are curious, keep reading and we will cover what these numbers mean next.

How are Tires Sized?

Tire sizing is split into three categories, each describing a different part of the tire’s dimensions. The categories are width, aspect ratio (A/R), and wheel diameter. We are going to break down what each category stands for below.

Tire Width

The first number is the width of the tread, which is the part of the tire that contacts the road. In the above example size, “235” means that the tire has a width of 235 millimeters.

Tire Aspect Ratio (A/R)

The second number represents the aspect ratio or the height of the sidewall. The sidewall is measured as a percentage of the tread width. In the above example, the number 35 after the slash means the tire’s sidewall height is 35% of the tread width. A lower aspect ratio correlates with a lower profile tire.

Wheel Diameter

The final number in the sequence represents the diameter of the wheel the tire is mounted on in inches. In the above example tire, the 17 indicates the tire fits on a 17-inch wheel.

What Do the Letters Mean?

You probably noticed the letters mixed into the size numbers. The first letter represents tire type, and the second number indicates the construction.

Tire Type

The very first letter(s) in the tire sizing represents the intended market and vehicle type for the tire. In the above example, P stands for P-Metric, which means the tire meets passenger car standards in the United States.

If you see “LT”, the tire is intended for use on light trucks and will often have higher pressure requirements than P-rated tires.

If a size rating has no starting letter, it is a European Metric tire. There are some differences in load capacity between European and P-Metric tires.

Tire Construction

Unless you are dealing with trailer tires, you will almost only see an “R”, which stands for radial construction. This article goes over the other types of tire construction out there.

Matson Point S is Your Source for Tires!

Our tire shop in Riverton is ready to help you with your next tire purchase, no matter the size! In addition to tires, we offer full-service auto repair and maintenance. Whatever your automotive needs, the team at Matson Point S will keep you moving. Call or schedule an appointment online today!


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