Tires 101: Sidewall

from Toyo Tires

ABOUT THE SIDEWALL

The sidewall of a tire includes a variety of important information. The numbers and letters identify dimensions and performance standards that allow you to compare tires more accurately and efficiently. This diagram will help you to understand those numbers and letters. For assistance in selecting a replacement tire, always consult your Toyo Tires dealer.

LOAD INDEX

The load index number and speed symbol correspond to the maximum load-carrying capacity of the tire and its maximum speed capability.

The load index is an assigned number that corresponds with the load-carrying capacity of the tire. For example, “96” indicates a load-carrying capacity of 1565 lb. at maximum inflation pressure. The load index for most passenger car tires ranges from 75-100.  Click here to view the complete load inflation index.

Load Index Chart

Speed Symbol Chart

Speed ratings are determined by indoor laboratory testing methods, which measure high-speed tire durability under controlled test conditions. These test procedures do not take into account underinflation, tire damage, vehicle characteristics or road conditions which can lead to sudden tire failure or loss of vehicle control at much lower speeds than indicated by the tire’s speed rating.

When replacing tires on your vehicle, you should use replacement tires with a speed rating equal to or greater than that of the original equipment tires if the speed capability and handling characteristics of the vehicle are to be maintained. Remember to never operate your vehicle in an unsafe or unlawful manner. Your Toyo Tires dealer can provide you with more information on speed ratings.

DIAMETER

The diameter indicates the size of the wheel from one side to the other. You can learn more about changing the diameter of the wheels of your car in the Plus Sizing section.

RADIAL

The “R” stands for “radial,” indicating the tire has radial construction.

ASPECT RATIO

The aspect ratio is the dimensional relationship of the section height to the section width. The lower the aspect ratio, the shorter the sidewall and the wider the shoulder-to-shoulder width.

WIDTH

The width of a tire is referred to as its section width. This is the width of an inflated tire in millimeters at its widest point from sidewall to sidewall.

The section height of the tire is measured in millimeters also. The section height is approximately the distance from the rim to the tread surface of the tire when it is not carrying any weight.

TIRE TYPE

Tires with a “P” are for passenger car use. Some passenger car tires may not have a “P” and are considered hard-metric tires. Some light trucks and SUV’s are equipped with original equipment P-metric or hard-metric tires.

Tires with a “LT” are for light truck or SUV use only. The “LT” designation stands for “Light Truck.” These tires are intended for more severe use often seen on trucks and follow load and inflation standards established by the Tire and Rim Association (TRA). Load Index values and load capacities for these tires can be found in TRA manuals.

Other Designations

Mud and Snow

The “M+S” indicates the tire is designed for mud and snow applications. The Mud and Snow designation may also appear as “M&S” or “M/S.”

 

Mountain Snowflake

The mountain/snowflake designate a tire designed for severe snow conditions.

Read the rest of this article here.