Tires have a lot markings on their sidewalls. Most of us know the basics, but in the next 11 minutes, we'll all become absolute know-it-alls about how to read just about every letter and number on a tire's sidewall.
Guiding us on this journey of tire decoding is explainer-in-chief, Jason Fenske of Engineering Explained. He gets into some stuff that one editor who formerly sold tires didn't even know.
First up, however, are the basics. The subject used in the video is a Michelin Pilot Sport 4 S tire that reads 235/35 ZR20. Those numbers denote millimeters, percentage, and inches, in that order. Jason points out that sometimes there's a P or LT in front of this combination of numbers and letters. This stands for either Passenger Car or Light Truck tire. The latter means the tire is engineered to withstand extra payloads or towing and hauling.
The 235 is the width of the tire from sidewall to sidewall in millimeters. The 35 represents the aspect ratio of the tire or the sidewall's height as a percentage of the tread width. This means the tire's sidewall is 35 percent of the tread's width, which calculates to 82.25 mm for the tire shown. Finally, the 20 represents the wheel diameter in inches, which means this particular tire is made for a 20-inch wheel.
What about the ZR? Looking at the R first, it represents the construction. We know tires are made out of rubber and cord layers called plies. In this case, the R stands for radial construction, which means the plies are perpendicular to the center line. There may also be a D that denotes diagonal construction. The Z will come in play in a moment.
After the initial tire measurement reading, we see 92Y. The 92 represents the maximum load the car can carry. The range of load ratings is vast and each number corresponds to a chart that shows how many pounds a single tire can carry. In this case, the 92 means it can support 1,389 pounds. The Y is the speed rating, or the maximum speed the tire was designed to withstand and maintain.
Back to the Z. The letter used to designate the highest possible speed rating, and it meant the tire could withstand more than 149 mph. A Z rating still means a tire can handle more than 149 mph, but it is now broken up into W and Y sub-ratings. W stands for 168 mph and Y equals 186 mph.
Going around the rest of the tire, Jason looks at the maximum tire pressure rating; tire composition; treadwear, traction, and temperature ratings; and a few other obscure markings that will make you the trivia champ at that next Cars and Coffee. Nerd out over all the tire-marking details in the video above.