How to Read Tire Size

If you ever checked the air pressure on your tires, you might have noticed a series of raised letters and numbers marked on your tire’s sidewall. Believe it or not, there’s actually a good reason why they exist. These sets of raised markings indicate, among a number of things: the width, diameter, speed rating, and even where and when it was created.

Knowing how to read tires sizes can be useful the next time you’re in need of a replacement. At Faulkner Toyota Harrisburg, our service and parts center is dedicated to providing drivers throughout the Harrisburg, Carlisle, and Mechanicsburg region with state-of-the-art resources to keep their vehicle’s running at peak performance. Continue reading to learn more!

Tire Type

Aside from the tire’s brand and model, there’s a specific code that denotes five distinct aspects of the tire that include:

  1. Tire Type: The first symbol of the tire code will depend on the type of vehicle you drive but will always begin with a letter. “P” stands for “passenger vehicles,” while codes that begin with “LT” stand for “light truck”.  These codes follow the P-metric standard which is used in the United States and determines the tire’s load capacity.
  2. Tire Width: The next three symbols denote the width of the tire from sidewall to sidewall. This 3-digit number is based in millimeters so, if the tire reads, “P215” that means it’s a passenger tire that’s 215 millimeters wide.
  3. Aspect Ratio: After the 3-digit tire width you’ll see a slash mark followed by two numbers. This denotes the size of the tire’s sidewall. The bigger the number, the bigger the tire’s sidewall.
  4. Construction:  This single letter denotes how the tire is constructed. For instance, “R” means the tire’s layers run radially.
  5. Wheel Diameter: Finally, the last two numbers indicate the distance from one end of the tire to the other and tells you what size wheel the tire fits on.

You may also come across the letters Z, S, T, or W which indicate the tire’s specific speed rating. This lets you know the maximum MPH you can safely achieve while using the tire.


All tires in the US must have a US Department of Transportation marking before they can legally sold to consumers. This lets you know that the tire has passed all minimum safety standards and is road ready.

The TIN or “Tire Identification Code” is a 12-digit number that immediately follows the DOT marking and denotes the manufacturer’s location, size, and date which the tire was produced at the end of the code.

Visit Faulkner Toyota Harrisburg for All Your Tire Needs

At Faulkner Toyota Harrisburg, our team highly skilled technicians are here to help drivers throughout Harrisburg, Carlisle, and Mechanicsburg by providing honest and thorough care over the lifetime of your vehicle. If you have any questions concerning your vehicle’s tires or are due for a replacement, stop by during service hours or go online and schedule an appointment today!