What's in a Number? (What Tire Numbers Mean)
July 23, 2023
Please wait while the video is loading...
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.
Tire Warehouse Depot
250 N. Lapeer Rd.
Lake Orion, Michigan 48362
248-929-0699
Need Service?
More articles from Tire Warehouse Depot
TCB your PCV (PCV Valve Replacement)
April 13, 2025
Your gasoline engine goes through some exhausting work. Yes, it's truly exhausting, as in: it produces exhaust! And when your engine starts behaving like it's exhausted, such as running poorly or getting lousy fuel economy, the trouble may be something called a PCV valve. Did you know it's a ser... More
When it Comes to Air Filters, Change is Good (Clogged Air Filter)
April 6, 2025
Engine air filters may not seem like a big deal, but when theyre clogged up with dirt, dust, and insects, your engine could wind up choking for air and not delivering you the power and performance it was designed to give. There are actually a couple of air filters in your vehicle. One filters th... More
Your Vehicle's Other Power Plant (Alternator Replacement)
March 30, 2025
Your vehicle's engine is probably the first thing that comes to mind when you think of a power plant. But it has another power source that is vital as well: the alternator. The alternator is what puts out the electricity that powers such things as your lights, power windows, sound system, and na... More