What's in a Number? (What Tire Numbers Mean)
November 22, 2020
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.
Elite Tire And Auto Care
33729 Plymouth Rd.
Livonia, Michigan 48150
734.427.3100
Need Service?
More articles from Elite Tire & Auto Care
Vive la Differential at Elite Tire And Auto Care in Livonia
May 3, 2026
There are a lot of drivers in Livonia who are due for a differential service, but had never heard of a differential before. With front-wheel drive being so common in Michigan these days, the differential is just taken care of during a transmission service, so most Livonia folks don't even have... More
Smooth Operator (Shock Absorbers)
April 26, 2026
When you are comfortably headed down the road, you may not realize how many of the imperfections in the driving surface are being smoothed out, so you hardly feel most of them. You can thank your shock absorbers for a lot of that comfort, and its important to make sure you keep your shocks in go... More
Are Modern Vehicles Maintenance Free?
April 19, 2026
In our auto video today we'll be talking with Alan Peterson about myths surrounding automotive maintenance. You can lump these myths into the statement that "modern vehicles are so reliable, they are virtually maintenance free."Any good myth has some elements of truth. No offense to Livonia Big... More