How to read the sidewall of a tire? A complete guide to cracking the code

Tires are the only point of contact between your vehicle and the road, so their correct condition and maintenance are essential for road safety. In this sense, knowing how to read the sidewall of a tire will allow you to make informed decisions when choosing them, changing them or inspecting their condition.

The sidewall of a tire, that rubber sidewall that covers the inner core, is packed with coded information that reveals essential data about its characteristics, performance and origin. At first glance, it may seem like a meaningless set of numbers and letters, but by deciphering this code, you will be able to understand aspects such as width, height, type of construction, load capacity, speed rating and other relevant details.

Keep in mind that if you are looking for tires or automotive services, the best option for you is Performance Tire & Wheel, which offers its services in Gulfport, Biloxi, Diberville, Wiggins, Pass Christian, Ocean Springs, Long Beach, Bay St. Louis and surrounding cities.

Tire measurements in standard and metric systems

In the world of tires, there are two universal languages to express their dimensions: the standard system and the metric system. Each uses a combination of numbers and letters to convey crucial information about the size, construction, and type of vehicle the tire is designed for.

• In the standard system, the first number indicates the height of the tire, measured in inches from the base to the top. The second number represents the width, measured in inches from side to side. The letter R indicates the radial construction, the most common today. Finally, the third number indicates the diameter of the rim on which the tire is mounted, also in inches. Sometimes additional letters appear after the standard system. For example, LT means "light truck" and P means "passenger tire." These letters indicate the type of vehicle for which the tire is designed.
• In the metric system, the first number indicates the width of the tire, measured in millimeters (mm) from sidewall to sidewall. The second number represents the aspect ratio, a percentage that indicates the height of the flank relative to the width. For example, a tire with a 55% aspect ratio has a sidewall that measures 55% of the width. The letter R still indicates the radial construction, and the third number, as in the standard system, represents the diameter of the tire in inches.

How to read the sidewall of a tire?

The sidewall of a tire houses a series of crucial information presented in a specific format. To begin to decipher it, it is important to understand its basic structure. Imagine the flank as a book divided into sections, each containing specific information:

Width, profile and diameter

The first section of the sidewall, where the tire dimensions are located, is essential for choosing the right tire for your vehicle.

• Width: The width of the tire is measured in millimeters and is represented by the first three digits of the code. For example, in 205/55R16, the width is 205 mm. A wider tire generally offers greater grip and stability in the dry, but can also increase rolling resistance and fuel consumption.
• Profile: Profile, also known as aspect ratio, is expressed as a percentage and is indicated by the two digits following the width. In 205/55R16, the profile is 55%. It represents the height of the sidewall as a percentage of the width of the tire. A higher profile (e.g. 60% or 65%) offers greater comfort and shock absorption, while a lower profile (e.g. 40% or 35%) improves handling and dry grip, but may be less comfortable and noisy.
• Tire diameter: The diameter of the tire is measured in inches and is indicated by the last number of the code. On 205/55R16, the tire diameter is 16 inches. It is crucial that the tire matches the diameter of your vehicle's rim.

Construction types

The letter following the tire dimensions on the sidewall indicates the type of tire construction. The two most common options are:

A: Radial: This is the most used construction type today, both in passenger vehicles and trucks. Radial tires offer a number of advantages over bias tires, such as:

• Greater stability and control: The radial structure of the tire distributes pressure more evenly, providing better road grip and more precise handling, especially in corners and at high speeds.
• Lower rolling resistance: The lower internal friction of radial tires translates into lower fuel consumption and greater energy efficiency.
• Greater comfort: Radial tires are generally more flexible and absorbent than diagonal tires, which results in a smoother and more comfortable ride, especially on uneven terrain.
• Greater durability: The radial construction of the tire offers better resistance to wear and fatigue, which translates into longer tire life.

B: Diagonal: This type of construction is less common today and is mainly used on older or specialized vehicles. Bias tires are more economical than radial tires, but offer lower performance in terms of stability, control, fuel consumption, comfort and durability.

Load index

The load index is a number that indicates the maximum load a tire can withstand at a specific pressure. It is located after the tire dimensions and the letter indicating the type of construction, followed by a letter indicating the speed code. For example, 91H means that the tire can withstand a load of 615 kilograms.

It is important to choose tires with a load rating appropriate for the weight of your vehicle and the type of driving you do. If you frequently drive loaded or at high speeds, you will need tires with a higher load index.

Speed code

The speed code is a letter that indicates the maximum speed at which a tire can withstand the load indicated by the load index. It is located after the loading index. For example, in 91H, the H indicates that the tire can withstand a speed of up to 240 km/h.

It is important to choose tires with a speed code appropriate for the type of driving you do. If you drive at high speeds, you will need tires with a higher speed code.

Date and place of manufacture

The DOT (United States Department of Transportation) code is a sequence of numbers and letters that indicates the date and place of manufacture of the tire. It is located in the additional information section on the tire sidewall.

The first two digits of the DOT code indicate the country of manufacture. For example, US indicates that the tire was manufactured in the United States. The next two digits indicate the week and year of manufacture. For example, 0123 means that the tire was manufactured in the first week of the year 2023.

Additional information: Symbols and markings

In the additional information section of the tire sidewall, you can find various symbols and markings that provide additional information about the tire's performance and characteristics. Some of the most common symbols and markings include:

• M S: Indicates that the tire is designed for use in mud and snow conditions.
• AW: Indicates that the tire is an all-season tire.
• Temperature: Some tires have symbols that indicate the recommended operating temperature range.
• Traction: Some tires have symbols that indicate their level of wet and dry traction.
• Fuel consumption: Some tires have a label that indicates their efficiency in terms of fuel consumption.

It is important to read the additional information on the tire sidewall to better understand its characteristics and performance.

The best tires and the best service

If you are in the Mississippi area and are looking for tires or automotive services, remember that Performance Tire & Wheel is the best option for you. Always at the best prices and with the best attention. We have a wide variety of wheels and tires for all types of vehicles, wholesale and retail.