What's in a Number? (What Tire Numbers Mean)
December 17, 2023
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.
Spartan Tire Brighton
4880 Old U.S. 23
Brighton, MI 48114
8102277377
Need Service?
More articles from Spartan Tire Brighton
Save Your Tires and Fuel: Why TPMS Is More Than a Warning Lightc
November 1, 2026
You know that little light on your dashboard that looks like a tire? Dont ignore it. Its a lot more than a warning light. Its trying to tell you something that can protect your tires, improve your fuel economy and keep your vehicle traveling safely down the road. Its called TPMS. The abbreviati... More
Can This Tire Be Saved? A Guide to Tire Repair vs. Replacement
October 25, 2026
When something goes wrong with one of your tires, one of the first things that goes through your head is: Do I have to buy a new tire, or is it possible to save this one with a repair? Understanding when you can have a tire fixed and when you need it replaced can prevent you from driving an unsaf... More
Keep It Rolling Right
October 23, 2026
Keeping your tires rotated regularly is one of the simplest yet most important maintenance services you can perform on your vehicle. It is where each tire is moved to a different position: front to back, side to side. That rotation helps to ensure your tires wear evenly, which directly impacts sa... More