How To Read the da Vinci Codes on Your Tires

Tire numbers indicate size, speed rating, and many other things.

The numbers and letters written on your tires don’t hide any tips about finding the Holy Grail, as far as we know, but they do have critical info you’ll need to get the right set for your car. Tires affect every aspect of your car’s performance including speed, stopping, handling, and fuel economy. It pays to pay attention to them, and we’re going to help you understand how.

Tires are actually more complicated than they may seem. They’re not just bands of rubber fitted to a metal wheel to help funnel water away when it rains! They don’t know that tires are extremely complicated, multi-layered products that have decades of research and development built into them.

There are also a vast array of different types of tires, each of which has a varying set of capabilities. So how do you know what your tire can do? Beyond the labels of winter, summer, and all-season, a tire’s sidewall holds tons of information coded into what looks like a bunch of random numbers and letters. Except they aren’t random at all. 

Characters on tire sidewalls are not just for decoration, most provide information that can help you know your car better. Let’s dive into what the readings are and what they all mean. 

Read the Tires? What Are You Saying? 

On the side of every tire, there are a few sets of numbers and letters, each of which has a different meaning. For example, the side of the tire will have a code that looks something like this: 

P235/55R19 101H

Let’s break down what it all means.

P: This indicates the tire is on the U.S. P-Metric. Where you see the P might also be an LT or nothing at all. P means passenger car, LT means Light Truck, and nothing means it’s a Euro-Metric tire.

235: The 235 number is the width of the tire from the sidewall to the sidewall, measured in millimeters. 

55: This number indicates the aspect ratio of the tire’s tread width to the tire’s sidewall height, not the height of the whole tire and wheel. 

R: R stands for radial tire. This indicates that the tire’s layers of construction run radially. You might also see D for diagonal or B for bias ply.

19: The 19 indicates the diameter size of the wheel, in inches. So, 19 means it’s a 19-inch wheel.

101: The last digits might or might not be included on your tire. 101 indicates the tire’s load index, or how much weight it can support, but it’s not a direct measurement. In this case, 101 translates to 1,819 pounds. See the full load index chart on Goodyear’s website. Note: P-Metric tires and Euro-metric tires might have different load indexes.

H: This might or might not be on your tire, but the H is indicative of a speed rating. The ratings are as follows: 

  • L = 75 mph
  • M = 81 mph
  • N = 87 mph
  • P = 93 mph
  • O = 99 mph
  • R = 106 mph
  • S = 112 mph
  • T = 118 mph
  • U = 124 mph
  • H = 130 mph
  • V = 149 mph
  • W = 168 mph
  • Y = 186 mph
  • Z = 149 mph+
A close-up of a tire sidewall on a Kia Telluride.
Sidewall codes tell a tire’s life story. – Image: Kia

Those Aren’t the Only Numbers and Letters I See, What About the Others?

Your tires have a lot of information displayed right on the rubber.

DOT AP 88 05CX 2519

DOT stands for Department of Transportation. When you see a set of letters and numbers that start with DOT, that’s the U.S. DOT Tire Identification Number, which can be between 6-13 letters. This can tell you numerous things about your tire.

  • AP: These letters indicate the manufacturer’s plant code where the tire was produced.
  • 88: These letters indicate the tire size code.
  • 05CX: These letters indicate the manufacturer construction code.
  • 2519: These letters indicate when the tire was produced. The first two numbers tell the week number during which the tire was produced, and the second two numbers indicate the year. So, 2519 means the tire was produced in the 25th week of 2019. 

M+S

M+S signifies the tire is designed for some level mud and snow capabilities.

Max Pressure

If your tire says Max Pressure 35 PSI, you should not increase your tire pressure higher than 35 PSI.

Max Load 

This number indicates the maximum poundage a tire can hold and carry.

Treadwear 240

This code estimates how long the tire should last.

Traction A

This code estimates the tire’s ability to stop a car on wet pavement.

Temperature A

This code estimates the tire’s resistance to heat.

The front wheels of a Genesis GV80.
Tire sidewalls can tell you the maximum load the tires can withstand. – Image Genesis

The Questionnaire

You’ve got questions, Car Bibles has answers!

Q.Why Do I Need To Know This Stuff?

A. This information could come in handy for several reasons. It could help you determine how much weight you can carry, it could help you determine what wheels you need, or it could help you determine how old your tires are, among several other things. It’s good to know, trust us.

Q. How Do I Check My Tire Tread?

A. The quickest method that can be done anywhere without specific tools is the quarter check. Flip a quarter upside down and place it in between the tire’s tread. If you can see the top of Washington’s dome, your tread is too worn and you need new tires. Do this across multiple parts of the tire to check tread, because tire rubber wears unevenly most of the time.

Q. Do Tires Expire?

A. According to the National Highway Traffic Safety Administration (NHTSA), tires do expire six years from their manufacture date.

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Tony Markovich

Tony MarkovichTony has a thing for pop-up headlights. His first car was a $3,000 1996 Saturn SC2 Coupe, and his current project is a 1970 Opel GT junker. When he's not daydreaming about the Cadillac Sixteen, he's watching the Chicago Bulls go undefeated on TNT. Contact the author here.