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How to Read Tire Sizes?

Several times in your vehicle’s lifespan, you’re going to have to change the tires. Even with the proper alignment and care, tires will eventually wear down and need to be replaced. When it becomes your time to change your tires, you need to make sure your replacements are the proper size.

At Montgomeryville Nissan, we want you to take the best care possible of your vehicle, so it’s important that you get the right tires. You might think that tire sizes shouldn’t be too hard to read, but without the proper knowledge, it’ll just look like a jumble of letters and numbers.

Reading Tire Sizes

For the sake of this guide, we’re going to use a sample tire size. The 2017 Nissan Maxima SR requires P245/40R19 size tires. Each portion of this series of numbers and letters has a meaning that’s easy to decipher if you know what to look for. Learn more about each of the sections.

Tire Service Type

The first letter in a tire size indicates the service type. When you see the letter P, it means the tire is for a passenger vehicle. If you drive a car, minivan or light pickup truck, you’ll find a P at the head of your tire size. When you look at our Maxima sample, you’ll find a P at the beginning which is to be expected for a sedan (P245/40R19). If you drive an SUV, heavy duty pickup truck or a full size van, you might see the letters LT at the beginning, which stands for light truck. There are other characters as well for spares and commercial vehicles.

Tire Width

Following your service type letter will be a three-digit number. This number indicates the cross-sectional width of the tire measured in millimeters. Looking at our Maxima example, we can see that the width of the tire is 245 millimeters (P245/40R19). Most tires for the average car will be around this number. If you need to convert it to inches, just divide the number by 25.4.

Tire Wall Aspect Ratio

Next in your tire size, you’ll see a slash followed by a two-digit number. This number represents your tire’s aspect ratio or the measurement of the sidewall distance relative to the section width. For example, the 40 in our Maxima tire size indicates that the distance from the outer tread to the wheel rim is 40% of the section width (P245/40R19).

Tire and Wheel Diameter

The final two-digit number indicates the size of the wheel the tire is meant to fit. You will find an R before this number (P245/40R19), but that just indicates that your tire has radial construction. You’re virtually guaranteed to have a tire constructed this way as 98% of tires on the market bear this R. The number following is more important. Referring to our Maxima example, the tire should fit a 19-inch wheel (P245/40R19).

Visit Montgomeryville Nissan’s Service Center

Now that you know how to read tire size, you’re prepared to get your tires replaced when it’s time. For the best auto service in the Philadelphia, Lansdale and Doylestown areas, look no further than Montgomeryville Nissan’s Service Center. Our service department is staffed by highly trained professionals who are prepared to handle any issue you might have. Visit or call us to schedule your service appointment today!