Back to all

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

March 12, 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.

Star Lube Branson
598 State Hwy 165
Branson, MO 65616
417-239-2886
https://www.starlubebranson.com

Need Service?

Request a Quote

More articles from Star Lube & Tire of Branson

Differential Essential (Differential Fluid Exchange)

April 20, 2025

What's the dif? To an automotive technician, it's the differential, a part of your vehicle that helps direct power from the engine to the wheels. The differential is a gearbox that enables the drive wheels to turn at different speeds (they do that when you turn). Inside the differential is a f... More

Flat Tire? Three?s the Charm (Tire Repair)

April 13, 2025

For most drivers, at some point youre going to have a flat tire. Depending on how it was damaged, it may have to be replaced. But sometimes, a repair will do the trick, as long as the puncture isnt on the sidewall and the hole is smaller than inch/6.35mm in diameter. Here are the three common w... More

Don't Do It Yourself (Perils of DIY Vehicle Repair)

April 6, 2025

Your vehicle is a complicated machine, and yes, it would be nice if you could take care of all of its problems yourself. There was a time when vehicles were simpler and it wasn't too hard for a weekend mechanic to replace brakes, adjust a carburetor or perform a tune-up. But vehicles are far mo... More