You’ve probably seen the size code on your tire’s sidewall. But what do all those letters and numbers mean? Here’s a quick breakdown of the basic information.

Let’s take for example P265/60R18. This code gives you the following information about your vehicle’s tire:

P = Passenger Tire (Light Truck Tires will begin with the prefix LT).

265 = Section Width in millimeters (measured at the widest part of the tire from sidewall to sidewall)

/60 = Aspect Ratio or section height to width ratio as a percentage. For this example, the side wall is 60% of the section width of the tire (265mm x .60 = 159mm). Therefore, the sidewall height is 159mm.

R = Radial Tire

18 = This is simply your rim diameter in inches. Why do we mix inches and millimeters? The world may never know.


Truck Tire Sizes are indicated a little differently. For example, let’s look at 11R22.5. In this example, the information includes:

11 = Section width in inches

R = Radial Tire.

22.5 = Rim diameter and rim type. Rims with .5 in the size indicate tubeless or drop center rims, while rim sizes that are whole numbers indicate multi-piece tube style rims.

There are other codes on the tire that indicate load index and speed rating, but that’s a topic for another day.

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