What's in a Number? (What Tire Numbers Mean)
October 27, 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.
Kwik Kar Saginaw
1216 S. Blue Mound Rd.
Saginaw, TX 76131
817-231-1700
http://www.kwikkarsaginaw.com
Need Service?
More articles from Kwik Kar Saginaw
Rumble from Down Under (Muffler Replacement)
May 10, 2026
Weve all noticed them at one time or another on the street: a car or truck that drives by and the deep roar from their exhaust system sounds like a drag racer on the line. But what happens when that rumble is coming from under YOUR vehicle? Well, it could be a sign your muffler needs attention. ... More
(Timing Belt)
May 3, 2026
You may have heard about an important part of your vehicle's engine called a timing belt, and many know that if that belt breaks, it can cause some very serious engine problems. Not all vehicles have them, and the ones that do generally have smaller engines. The timing belt keeps the engine sy... More
Lubricate Driveshaft
April 26, 2026
See if any of these are happening to your vehicle. You feel it vibrating excessively underneath when its running, or you hear strange clunking, grating, or grinding sounds coming from beneath. Maybe its hard to turn your vehicle, or you can hear squeaking when youre going slow. Perhaps you fee... More