How to Read the Tire Size Code

If you’ve ever tried to decode the strange string of numbers and letters stamped on the side of your car’s tires, chances are you ended up entirely mystified – and for good new tiresreason. The tire size code is precisely that – a code – and it doesn’t give up its secrets as easily as you might hope.

Deciphering the Tire Size Code

There is quite a bit of information encoded in that short string of characters, but it’s not too difficult to figure out what it’s trying to tell you. We’ll use the sample code P215/60R16 94V, which is a common tire size for the Honda Accord.

Most tire codes start with a letter. The “P” on our Honda Accord’s tire indicates that it’s a passenger vehicle type wheel. Just about every car on the road – except for big trucks – will have a “P” designation in their tire’s code. A “T” indicates that the wheel is a temporary spare – which shouldn’t be on your car unless you’re on your way to an automotive service center. Some trucks use “LT” tires.

The first number is the measurement is in millimeters and denotes the tire’s sectional width, or the distance from one sidewall to the other. After that number there should be a slash followed by another number. That number indicates the length of the sidewall height as a percentage of the sectional width.

Next, there will be some combination of letters. An “R” or a “D” indicates the type of tire construction – either radial or diagonal. If there’s an “F” after the “R” or “D,” the tire features run-flat technology. A “Z” before the “R” or “D” indicates that the tire is rated for a speed above 149 mph. The number after that is rim diameter of the wheels that the tire is made for.

The separate number/letter combination at the end indicates the load index and speed rating of the tire: a higher number means a higher load limit, and a letter that comes later in the alphabet indicates a higher speed rating (excluding “Z”).

Need New Tires?

If you just need a new set of tires, it’s easy enough to just bring your car into your local Orland Park auto service center. But if you’re looking to find out a bit more about your tires, the tire size code is a great place to start.