Back to all

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

April 20, 2025

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 Tire & Auto Service Center Millard
4870 S 137th Street
Omaha, NE 68137
402-895-4274
http://www.tuffymillardave.com

More articles from Tuffy Millard

U and your U-Joints (Lubricate U-Joints)

September 7, 2025

If your vehicles power goes to the rear wheels, then you have something called U-joints in the drivetrain. U-joints are connectors that allow the rotating power from your vehicles engine to deliver its power through a driveshaft to make the rear wheels rotate. You need U-joints because the surfa... More

Smooth Operator (Shocks and Struts)

September 1, 2025

Few of us ever drive somewhere without encountering some pretty rough roads, and it's amazing how well our vehicles are able to smooth out the ride. Thank your shocks and struts. The two parts are similar. Some cars have shocks in the rear, and struts in the front. Others have struts all around... More

Steering You Right (Power Steering Fluid Service)

August 25, 2025

Its important for safe driving that two of the most important systems in your vehicle work right. One is the brakes. The other is the steering. Nearly all vehicles on the road have some sort of power steering that allows you to direct a very heavy machine with little effort. There are two ty... More