What's in a Number? (What Tire Numbers Mean)
December 27, 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.
Top Tech Auto Repair Royal Oak
3110 Rochester Rd
Royal Oak, Michigan 48073
248-585-0980
http://www.toptechautorepairroyaloak.com
Need Service?
More articles from Top Tech Auto Repair Royal Oak
Why You Have an O2 Sensor (Oxygen Sensor)
November 30, 2025
If someone asked you what gas made up the largest portion of the atmosphere, what would you guess? Well, it's not oxygen; it only makes up 20.9 percent. But since we're talking about oxygen, you should know that your vehicle uses oxygen sensors to make sure your engine is running the way it shou... More
Cold Weather Vehicle No-Nos (Items to Avoid Storing in a Freezing Vehicle)
November 23, 2025
It's always easier to leave a few things in your vehicle so you'll have them on hand. But in cold weather, while it's a good idea to carry items such as a phone charger, blanket and shovel, there are some things you shouldn't store in your vehicle. Medicines and drugs. Cold temperatures can af... More
10 Things That Are Lowering Your Fuel Economy
November 16, 2025
Regardless of whatever current gas prices may be, if you could use less gas, wouldnt you? Well, here are 10 things that are robbing you of better fuel economy that you can change for the better: Not enough air in your tires. Underinflated tires have a smaller rolling diameter and more res... More