Have you ever taken a close look at your tire’s sidewall? If so, you may have noticed a collection of numbers and letters circling the edge near the center. Do you know what they imply about your tires? A large majority of drivers have little idea regarding what these codes represent. It’s worth investing the time to become familiar with them; they offer a lot of useful information.

Below, we’ll provide a crash course on the most important markings displayed along your sidewalls. For a point of reference, we’ll start with the largest among them, which may look similar to “P225/50R15 92V”. Use the following guide whenever you need to know what a specific code means.

Analysis Of The Code “P225/50R15 92V”

Notice the “P” at the beginning of the code. The letter defines the type of tire. “P” means it is designed for passenger vehicles; “ST” means it is suited for a “Special Trailer”; and “LT” means “Light Truck”. If you do not see a letter, the tire is likely a European product.

The “225” measures the distance in millimeters between the sidewalls. The measurement is taken cross the widest point from one edge to another.

The “50” is an aspect ratio. It defines the ratio between the tire’s sidewall height compared to its width. “50” means the height is 50% of its width, or half of 225 millimeters.

The letter following the aspect ratio indicates the type of construction used when creating the tire. “R” signifies “Radial” (the standard); a “D” means “Diagonal”; and a “B” indicates “bias ply” construction.

Note the “15” following the “R” in our example code. This number represents the diameter (in inches) of the wheel’s rim.

The “92” is the tire’s load index. It indicates the maximum weight capacity of the tire, and usually ranges between 75 and 105 for most passenger tires. In this case, the “92” corresponds to 1,389 lbs. on a standard load index chart. It’s worth mentioning that the maximum weight capacity reflected by the index is for that particular tire, not the entire set.

Lastly, the “V” in our code indicates the tire’s speed rating. It reflects the maximum speed at which the tire can be safely used for a prolonged period. In this case, the “V” corresponds to 149 mph. Driving at faster speeds will introduce a risk of a blowout. As a side note, this rating is assigned by the U.S. government after the tire undergoes a series of tests that prove it meets minimum standards.

All tires also have a DOT code. This marker is mandated by the Department of Transportation, and reflects several details, including the tire’s manufacturer and age. The age is displayed with four digits; the first two digits denote the week, and the last two digits denote the year. For example, “1908” means the tire was manufactured on the nineteenth week of 2008.

If you look closely near the edge, you’ll see a value (e.g. 40 psi) that reflects the maximum air pressure your tire can withstand. Exceeding this amount will risk a blowout.

You’ll also notice a tread wear rating. This rating is a numeric value between 100 and 200 that reflects the durability of the tire’s treads. 100 is the baseline, or index. It’s important to note that this rating only reflects the anticipated life of the treads compared to other treads. That is, a tire with a tread wear rating of 160 will last longer than one with a rating of 120 given similar driving surfaces and conditions. But this does not address the actual predicted life of either tire.

There is a wealth of information printed along the sidewalls of your tires. While it is not essential to know what is there, the markings can provide insight into your tires’ durability and capacity.

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Category: Automotive
Keywords: tires, sidewall, tire sidewall, tire markings, what tire markings mean