Back to all

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

July 31, 2022

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 Fort Myers (Colonial Blvd)
3263 Colonial Blvd
Fort Myers, Florida 33966
239-277-7655
https://www.tuffycolonialblvd.com

More articles from Tuffy Fort Myers (Colonial Blvd.)

Why is My Brake Pedal Hard to Push?

November 2, 2025

When you push on your brake pedal, you should find your vehicle easy to stop. But at some point, you might notice stopping takes much more pressure on the pedal than it used to. When it gets to that point it becomes a safety issue, and you should bring your vehicle in so we can track down whats... More

"Current" Affairs (Blown Fuses)

October 27, 2025

You may be driving along and find that suddenly your radio stops working. There are no numbers on the display. Then when you get home, you notice the garage door opener doesn't do a thing when you press the button. Hmm, this was working just fine this morning. Are the two problems somehow rela... More

Hold the Oil! (Oil Pan Gasket Replacement)

October 23, 2025

You've likely heard how important oil is to your vehicle's engine. Did you know that there's one part that's responsible for holding that oil so you can use it every day? It's called the oil pan, and it sits at the bottom of the engine. The oil pan is a vital, though simple, part of your engine's... More