How to Read Tire Size

How to Read Tire SizeWhen you look at your tires, you probably notice a string of seemingly meaningless letters and numbers. Yet, a service technician can look at that same string and know everything about your tire from type and size to how it was made.

You, too, can learn how to read tire size, thanks to this quick guide from Elite Acura. Keep reading so you can know what’s going on the next time you’re shopping for new tires in Maple Shade, Moorestown, and Cherry Hill.

Throughout this guide, we’ll use P235/55 R19 as an example. This is the tire size that comes standard on the base model of a 2019 Acura RDX.

Tire Type

Tire TypeThe tire size generally begins with a letter that lets you know what kind of vehicle it was created for. P is short for “P-metric,” and means the tires were designed for use on a passenger car. LT, on the other hand, stands for “LT-Metric” and means the tires were created for a light truck.

If you simply see at T, on the other hand, you’re looking at a spare tire: The T stands for “temporary.”

As you can see, our sample tires were created for a passenger car: P235/55 R19.


The three-digit number immediately following that first letter describes how wide the tire is from sidewall to sidewall, when mounted. This is measured in millimeters.

So, in our example—P235/55 R19—this tire is 235 millimeters wide.

Aspect Ratio

Next up is a slash, followed by a two-digit number that tells you how high the tire is compared to its width—in other words, its aspect ratio. A larger aspect ratio corresponds to a higher-profile tire, and vice versa.

On our example—P235/55 R19—the height of the sidewall is 55% that of its width. So, we can expect this tire to be about 129 millimeters high.


Tire ConstructionAfter the aspect ratio, you’ll see a letter that says how the tire was constructed. The vast majority of passenger tires use radial construction, indicated with an R. On rare occasions, you may see a B (for belted-bias) or D (for diagonal-bias).

As you can see, our P235/55 R19 tires were made using radial construction.

Wheel Size

Following the construction indicator is another two-digit number. This lets you know what size wheels the tire fits. Car wheels, or rims, usually range from 16 to 19 inches. The P235/55 R19 tires in our example should go on 19-inch rims.

Additional Information

We’ve reached the end of our Acura RDX tire size, but if you’re looking at the sidewall of your current tires, you may see additional information after the wheel size.

First up is a load index, which lets you know how much weight the tires can safely carry when properly inflated. Most car tires have a load index between 75 and 100.

You’ll need to use a load index chart to find out the weight that corresponds to each number. For instance, a load index of 75 means that tire can carry up to 852 pounds. A tire with load index of 100, meanwhile, can carry 1,764 pounds.

Multiply this number by four—the number of tires on your vehicle—to see how much weight your car or truck can safely carry with these tires.

Lastly, a letter rating lets you know how fast the tires can safely travel. The farther in the alphabet, the higher speed that tire can safely travel. For example, Q-rated tires can travel up to 100 MPH, while V-rated tires can safely travel up to 149 MPH. Again, you’ll need to look up a chart to see what each letter means.

Visit Our Tire Center

Now that you know how to read tire size, you’re ready to start shopping for new tires for your car!

If you’re in Maple Shade, Moorestown, or Cherry Hill, visit our tire center at Elite Acura. We’ll help you choose the right tires for your vehicle and install them for you, so you can get back on the road with peace of mind.

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