Back to all

What's in a Number? (What Tire Numbers Mean)

October 6, 2024

You've probably never paid much attention to the writing on the sides of your tires, but they contain a wealth of information.  There's a long combination of letters and numbers that can tell you a whole lot about what tires your vehicle was designed to be riding on.  Let's check out this example found on an SUV: P245/70R17 108T.

The first letter, P, means it's intended for passenger vehicles.  If there's no letter, it means it's a metric tire.  If there's an LT at the beginning or end that means a tire designed for light trucks.

Moving on to our example, the 245 shows how wide the tire is in millimeters from sidewall to sidewall.  The number that follows in our example, 70, means the height of the tire is 70% of its width.  The letter after that in our example, R, describes the type of tire (on this vehicle, radial).  Following that is the diameter in inches, in our SUV example, 17 inches. 

How much load the tires' sidewalls are designed to take is what that next number is all about (108 in our example).  The higher the load index, the more weight the sidewalls can take.  And the last letter is the speed rating of the tire, in our example, T.  The further along in the alphabet that letter is, the higher its speed rating.  So now you know what those letters and numbers mean.  But why are they important?

When you are getting ready to replace those tires, those numbers are telling you what the original equipment was when your vehicle was new.  Sticking with the same rated tires is always a good idea.  If you don't know what you're doing, trying different sized tires and wheels can cause real issues when it comes to performance and safety, considering all the computerized systems now found on vehicles.  When in doubt, consult your service advisor when it comes to buying new tires.  He or she knows what those tire numbers and letters mean… and a whole lot more.

Tuffy Lake In The Hills
59 West Acorn Lane
Lake In The Hills, Illinois 60156
847-854-9850

More articles from Tuffy Lake in the Hills

Giving CV Joints the Boot! (CV Joint and Boot Replacement)

August 31, 2025

Ever wonder how your vehicles transmission is connected to your wheels? After all, when you hit a pothole or some other uneven part of a roads surface, there has to be something that can maintain the connection between the transmission and the wheel yet keep everything moving at the same speed. ... More

Greeted by a Screech (Loud Noise when Starting Vehicle)

August 24, 2025

No one likes to be greeted in the morning by having someone screech at you. The same goes for a loud, high-pitched noise your vehicle greets you with every time you start the engine. If you're wondering if that's normal, no, it isn't. And it is worth getting checked out. The good news is that... More

Catalytic Converter Replacement

August 17, 2025

Many of us have become aware of how important it is to keep our planets air clean, and your vehicle has a key component that helps do just that: the catalytic converter. Its in the exhaust system, and its job is to superheat unburned, harmful byproducts in the exhaust, so they dont get spewed ou... More