Understanding Tire Sidewall Markings

Posted on January 16, 2022 in Tire Repair

How to Properly Read Tire Markings

It’s a smart decision to check your tires for wear and tear routinely and to ensure they have enough air. During your inspection, you might have noticed a sequence of numbers and letters on the sidewall of the tire. These markings are much more important to understand than you might think.

These letters and numbers tell you if the tires meet the safety standards of the U.S. Department of Transportation (DOT). They also indicate the Uniform Tire Quality Grading (UTQG) and the speed, load, and maximum tire pressure specifications.

The tire repair technicians at Auto Clinic of Maryland in Finksburg, Maryland, can further explain these critical tire markings.

P = Passenger Car Tire

The very first letter in the sequence indicates the class of the tire. P means that the tire is a passenger car tire. If there’s an LT, the tire is a light truck tire.

250 = Section Width Tread (mm)

The next set of numbers on your tire’s sidewall is the width of the tire from one sidewall to the other. It’s measured in millimeters (mm). In our example, 250 indicates that the tire is 250 millimeters wide.

50 = Aspect Ratio

This is the height of the tire’s sidewall, which is the percentage of the section width. For instance, the sidewall height is 50% of the 250 section width from the example listed above. This equates to 125.

Z = Speed Rating

This number is the maximum speed at which the tires, when properly inflated and installed, can be driven on.

R = Radial Construction

This indicates that the tire is a radial tire. These types of tires have layers of fabric with cords that run at right angles to the tire’s circumference. The tread is supported by additional layers around the circumference. Radical tires are the most common type of car tires.

20 = Wheel Diameter (inches)

This specifies the size of the wheel that fits the tire in inches. In our example, the tire fits a 20-inch wheel.

100 = Load Index

This specifies the maximum load the tires can support. It’s critical to install tires that meet or exceed the manufacturer’s specifications of your vehicle.

Do You Need Tire Repair?

If you’re in the market for tire repair or replacement, call Auto Clinic of Maryland in Finksburg, Maryland, today at (410) 876-6313. We’ll quickly fix or replace your tires and get you back on the road in no time!