How to Read Tire Sizes


In order for Wexford, Pittsburgh, and Cranberry Township drivers to know which tires match their car, they need to learn how to decode the numbers and letters on the tire sidewall. Once you can read this, you’ll know how to read tire size.

If you’re not familiar with the code, check out this article by Baierl Tires. We make reading tire size easy with a simple breakdown.

Decoding Tire Size

The string of letters and numbers on your tire’s sidewall may not hold a lot of meaning to an automotive novice. However, each of those pieces represents a different factor of your tire’s size and performance. Let’s dig into each, going from left to right:

Tire Type

At the beginning of the tire size, you’ll see a letter indicating what kind of tire you’re working with.

  • P: This is a passenger tire.
  • LT: This is a light truck tire.

The Tire Width tire sizes

The next three numbers in the series represent the tire’s width from sidewall to sidewall (measured in millimeters). If the number you see is 195, as an example, that would mean that the tire is exactly 195 millimeters wide.

The Aspect Ratio 

A forward slash will follow the width, and after that comes the tire’s aspect ratio. What does this mean? It’s the ratio of the height of the cross-section to the width. In the simplest terms, a bigger aspect ratio means that your tire’s sidewall is going to be a lot bigger, too. You’ll see larger numbers on big vehicles like trucks or vans.

The Construction

Next, there will be a single letter representing the construction. Typically, you’re going to see the letter “R,” which means the layers of the rubber run radially.

The Wheel Diameter

If you measure your wheel from end to end, what you’ll have is the wheel diameter or the next numbers in the sequence. This is where we can truly determine the size of the wheel (something that is of the utmost importance when finding a fitting tire). If the number were 20, we’d need a wheel with a diameter of 20 inches.

The Load Index

The last two numbers after the diameter are the load. This is the weight your tire can support when inflated (according to your owner’s manual).

The Speed Rating

How fast can your tire go? This last letter will tell you via a rating system. The tires your car comes with will let you know what speed rating you need to stick to, and you should make sure all your tires match this. Here are a few examples of common ratings:

  • R (top speed of 106 MPH): Good for light trucks.
  • S (top speed of 112 MPH): Good for family sedans.
  • T (top speed of 118 MPH): Good for minivans.

How to Choose Tire Size tire rotation service

When it comes to choosing the right size tires for your car, there are two easy ways to do it (aside from decoding the sidewalls):

  1. Consult the owner’s manual. This should have the information you need.
  2. Speak to the experts at your local tire shop. They can point you in the right direction.

Schedule Your Tire Appointment Today

At Baierl Tires, we offer a wide selection of factory-direct tires to drivers in the Pittsburgh, Wexford, and Cranberry Township areas. When your vehicle is ready for a new set, just talk to one of our team members to find the right size.

Contact our team online or over the phone to schedule a tire replacement today!

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