How to Read Tire Size

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A lot of the explanations available for how to read tire size are unnecessarily technical and complicated, which let’s face it, kind of defeats the point. At Braman Honda of Palm Beach, we understand that our customers aren’t automotive experts. Rather, they’re just normal people who want to know more about how to take care of their vehicle.

In this article, we’ll simplify what your tire markings mean so that our customers in the Palm Beach, Wellington, and Greenacres areas can make sense of what they see on their tires.

How to Read Tire SizeTire Markings and Ratings

As the owner of the vehicle, the main markings you’ll be interested in are probably the speed rating, the load index, and the wheel size. These markings usually appear together in a string on the side of the tire sometimes separated by slashes. You might see a letter P or the letters LT at the beginning of the sting which designates the class of the tire. P stands for passenger car while LT stands for light truck.

The next number is the section width; this is the distance from sidewall to sidewall in millimeters. The next number is the aspect ratio, which is technical way of saying the height of the wheel in proportion to the width; this is always a percentage. So, if the number you see is 40, you know the height of the sidewall is 40% of the width of the tire.

This number may be followed by the letter Z, but more often than not you’ll see the letter R. Here, R stands for radial tire which is a very common type of tire for passenger cars and light trucks. If you see the letter Z, that means your tire has a speed rating of above 149 MPH, and you should also see a W or Y at the end of this series of markings. A W means your tire is rated for a max speed of 168 MPH, while Y is 186 MPH.

Typically, after the radial tire marking is another number that designated the proper wheel size for this tire. This number is expressed in inches. You’ll want to find a wheel that has the same diameter as stated here. Otherwise, the tire won’t fit.

Finally, you should see a number and letter combo finishing off this marking series. The number is a reference to the load index where each number stands for a certain weight. For example, if you see the number 80, the load index indicates this tire can handle 992 pounds. The letter following the load index number is the speed rating. Each letter represents a maximum speed the tire can be driven on.

More Tire Markings

The remaining markings and ratings on the tire will include the manufacturer name, as well as information for the U.S. Department of Transportation and the Uniform Tire Quality Grading. This manufacturer and safety information can be useful if trying to learn more about your tires, but isn’t important if you’re just trying to figure out what size and type of tire your vehicle needs.

If you live in the Palm Beach, Wellington, and Greenacres areas and have questions about how to read tire size, please contact our service team at Braman Honda of Palm Beach.