When it comes to tires, the writing is on the [side]wall. Literally. Tire sidewall markings—those seemingly random numbers and letters embossed on the side of your tires—can tell you a lot about not only your tires, but also your whole vehicle. Here’s how to read tire sidewall markings.
Class, Width & Aspect Ratio
The first letter on a tire indicates the tire’s class. For example, a “P” designates a tire as a passenger car tire, while an “LT” means the tire is meant for light trucks. Next comes the section width, which is the width of the tire from one sidewall to the other measured in millimeters. After the section width is the aspect ratio, referring to the height of the sidewall as a percentage of the section width.
Speed Rating & Tire Type
As you move along, you’ll next see the speed rating, which designates the maximum speed the tire can be driven when properly installed and inflated. “Z” is the highest speed rating. If you see an “R” after the speed rating, your tire is a radial tire. Radial tires have layers of fabric with cords running at right angles to the circumference of the tire and tread that is strengthened by even more layers, making it the most common type of automotive tire.
Diameter, Load Carrying Capacity & Speed Rating (Again)
Next in line is the wheel diameter, specifying the size of the wheel that the tire fits. Then comes the load carrying capacity in large print right after the diameter marking. It is very important to only install tires with a load index that meets or exceeds your vehicle manufacturer’s specification. Another speed rating generally appears as a single letter right after the load carrying capacity. The second speed rating denotes the actual miles per hour the tire is rated for.
Traction, Temperature & Treadwear
Modern vehicles have stock tires that undergo the Uniform Tire Quality Grade (UTQG) review, which analyzes the parameters of traction, temperature, and treadwear. The traction grade, ranging from AA to C, represents a tire’s ability to come to a full stop on wet and slippery roads. Next to the traction rating is the temperature grade. This represents how well a tire can resist and dissipate heat. Finally, the treadwear grade refers to a tire’s tread durability and longevity.
Ask Aardvark if You have Auto Questions
If you have concerns about your tires or any aspect of your vehicle, come to Aardvark Automotive and get your questions answered honestly and clearly. We fix what others can’t in Amarillo, TX!