What Do Tire Numbers Mean?

Whether you’re in need of new tires or you just want to understand what kind of tires are currently equipped on your vehicle, learning about tire number meanings can help you head out on the roads of New Canaan with confidence. But what do tire numbers mean, exactly? At first glance, a code like “P215/65R15 95H” is bound to appear mysterious, but Mercedes-Benz of Greenwich has all the answers you’re searching for.

Determining Tire Number Meanings

Tire number meanings can tell you (almost) everything you need to know about the design, construction, size, load index, and speed rating of your tires. Let’s take a closer look at the example we mentioned above–P215/65R15 95H–and find out how this tire number’s meaning breaks down.

What Do the Numbers on Tires Mean?

Decoding “P” – Vehicle Classification

P in this tire number stands for “P-Metric tire.” That means the tire is suitable for use on passenger vehicles–mainly cars and some crossovers. In place of this P, you might also see the letters “LT” (for light truck). If the first letter is missing, you’re dealing with a Euro-Metric tire.  The most important thing to know about the first letter in the tire code is that each classification corresponds to a certain load capacity range. If you’re equipping tires on a vehicle, make sure that they can safely handle your vehicle’s curb weight and payload.

Decoding “215” – Tire Width

“215” is the width of the tire from sidewall to sidewall, given in millimeters. This section of the tire number is almost always three digits long. If your tires are too wide for your vehicle, you’re obviously going to run into trouble.

Decoding “65” – Tire Height

Next you’ll see a forward slash, followed by a two-digit number. This two-digit number is your tire’s aspect ratio, i.e. the tire’s height presented as a percentage of its width. So, a number of “65” indicates that the distance from the wheel well to the edge of the tire is equal to 65% of the width of the tire–or roughly 140 mm in this example.

Decoding “R” – Type of Construction

“R” stands for “Radial Tire”. Radial is a type of construction which employs cords of polyester, steel, and fabric, coated with rubber. This type of tire is in use on almost all vehicles available today, so if you see another letter in this position, don’t hesitate to reach out to learn more.

Decoding “15” – Wheel Size

“15” in this position stands for “built for 15-inch wheels.” More precisely, this measurement is the wheel’s diameter, given in inches.

Decoding “95H” – Load Index and Speed Rating

Your load index is a more precise measurement of how much weight your tire can handle. A tire with a load index of “95” can handle up to 1521 pounds when properly inflated. Tires for passenger vehicles (see above: “P-Metric tires”) generally offer load indexes falling between 75 and 105, but other types of tires offer significantly higher capacities. What do the numbers on your tires mean? Any questions about load indexes can be directed to our service team. The “H” in this number represents your tire’s speed rating, i.e., how quickly you can travel without damaging the tire. A rating of H corresponds to a speed rating of 130 mph–much higher than any local speed limit. Spare tires, on the other hand, usually have lower speed ratings.

What About Your Recommended Tire Pressure?

Earlier we said that tire numbers could tell you almost everything you need to know about your tires–but as you can see, they won’t tell you your recommended tire pressure! For that, check your owner’s manual or look for a sticker in your driver’s side door jamb.  Most modern Mercedes-Benz vehicles include a tire pressure monitoring system (TPMS) that can help you determine when your tires need more air. Whether or not your vehicle possesses the feature, it’s a good idea to check your tire air pressure once every month or so. You should also keep up with tire maintenance as listed in the Mercedes-Benz service schedule! To get a precise measurement of your tire air pressure, pick up a tire pressure gauge from our parts department. We’re easy to reach from anywhere near Rye or Stamford.

Turn to Mercedes-Benz of Greenwich for All Your Maintenance Needs

While you’re here, learn more about DIY car care or explore a few of our other service tips and tricks. Whether you’re in need of new tires or you just want some help in keeping your current set well-maintained, it’s quick and easy to schedule service online.