What Do the Numbers on Tires Mean?

Closeup of Tire Numbers with Wheel Rim

As you’ve driven your Chevy on your North Haven commutes, you may have noticed a series of letters and numbers on your tires’ sidewalls. What do the numbers on tires mean? Keep reading to find out from the service team at Executive Chevrolet, your Wallingford Chevy dealer!

What do Tire Numbers Mean?

The code on the sidewall of any given tire indicates information including its purpose, type, size, and more. Making sure you have the right tires for your Meriden Chevy is the best way to ensure your safety and your car’s continued health.

Tire Number Meanings by Example

The best way to learn about tire number meaning is to break down an example code from front to back:

P 215/65 R 15 89H

Tire Application

Many tires have a letter at the beginning of their code. This letter indicates the tire’s intended use:

  • P (P-metric) tires have been designed to provide a smooth ride, good handling, and long tread life—perfect for passenger vehicles like cars, minivans, and SUVs.
  • LT (Light truck) tires are designed for heavier use, including more weight, uneven surfaces, and the like. You’ll find these on hard-working trucks and off-road SUVs.
  • ST (Special trailer) tires are designed for extra carrying capacity, but they’re not good for steering axles. That’s why you should only see an ST tire on a travel trailer, fifth wheel, or other trailer.

Our example tire above is designated P for passenger car usage.

What do Tire Numbers Mean Without a Letter at the Front?

Some tires don’t start with a letter at all. These are Euro-metric tires, and are rated for basically the same use-cases as P-metric tires.

Tire Width

The first number in the tire’s code indicates the tire’s width in millimeters. For our example tire above, the number 215 indicates that it’s 215mm wide.

Aspect Ratio

Next up, the number 65 indicates the tire’s aspect ratio, or the ratio of its cross-section height—from its inside rim to its outside—to its width. Our example tire is 65% as tall as it is wide.


A letter standing for the type of construction used is next. Tires can be constructed in a number of ways, including:

  • Radial construction, indicated by R
  • Bias-ply construction, indicated by B
  • Diagonal construction, indicated by D

The example tire above has been radially constructed, as we can see from the R on its sidewall. Radial construction is the most common type in modern tires.

Rim Diameter

Next, the tire tells us what wheel diameter it will fit. This tire will fit a 15-inch rim diameter wheel.

Load Index

The 89 in the example tire number indicates its load index rating. There’s a standard chart that lists all possible load indices and their weights, but 89 corresponds to a load capacity of 1,279 pounds when the tire is maximally inflated.

Speed Rating

Finally, a letter for the tire’s speed rating indicates the top speed that it’s safe to travel with this tire. Speed rating is almost always a single letter A–Z, and in our case H means the tire is rated for 130 miles per hour maximum speed.

How to Check Tire Pressure

While knowing the tire number’s meaning is important, the best way to keep your tires in top shape for as long as possible is by keeping them properly inflated. You can check your tire’s air pressure manually, but most modern Chevrolet models feature a Tire Pressure Monitoring System (TPMS) that will automatically alert you when your tire pressure is outside of normal operating range. When you get a TPMS alert, top off your tires yourself or bring your Chevy to our Wallingford service center for quick service at a great price!

Executive Chevrolet is Here For Your Chevy’s Maintenance Needs

Whenever you need maintenance or service on your Chevy, including new tires, oil changes, and more, bring it to Executive Chevrolet for all of your service and parts needs. We make it simple to schedule your service visit online, and our service specials help you save even more! Contact us today if you have any questions about what your tire numbers mean or anything else.


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