Tire Education Spotlight: Cooper Tire shares how to read a tire sidewall
By Andrea Berryman / Director of Product Development/ Cooper Tire & Rubber Company
The tire sidewall provides a lot of important information. You can help your customers understand this information, making them smarter about their tires and tire purchases, and helping you continue to be their trusted ally.
Here’s a breakdown of how to explain some important sidewall information on passenger vehicle tires for customers who may not be familiar with tires or have always wondered what this information means.
BEYOND THE SIDEWALL: PROPER TIRE INFLATION PRESSURE
This is one case where the vehicle owner must look beyond the sidewall for the right information. What is printed on the tire sidewall for inflation pressure is the maximum cold inflation pressure allowed in the tire, not the proper inflation pressure for the tire when fitted to a specific vehicle. The proper inflation pressure is provided by the vehicle manufacturer and can be found on the vehicle tire placard usually located on the driver side door jamb, glovebox or inside the fuel door of most vehicles. This sticker provides the correct inflation pressure for the vehicle’s tires.
Inflation pressure enables tires to support the load of the vehicle. Therefore, proper inflation is critical. The right amount of inflation pressure helps the vehicle and the tires achieve their optimum performance, last longer and even helps reduce fuel costs.
Note: tires heat up from driving, so do not check tire pressure immediately after a trip, no matter how brief. Wait a few hours until the tires have cooled.
The letters “M” and “S” indicate the tire is intended for limited mud and snow service. This mark may be found in several formats that may include: “MS,” “M/S,” “M&S,” or “M+S.”
MOUNTAIN SNOWFLAKE SYMBOL
The snowflake symbol inside a mountain range indicates how a tire will perform in the snow. If your customers drive in snow frequently, checking the tire’s sidewall to see if this symbol is present is very important. The three-peak mountain snowflake, or 3PMS, indicates that the tires were designed specifically for severe snow and can handle those conditions.
The load index is a numerical code (104/101 in the example image below) associated with the maximum load a single tire can carry at the speed indicated by its speed symbol (see below) under specified service conditions. The load index is a code ranging generally ranging from 50-129 that represents the maximum load carrying capacity for a single tire. In the example below, single and dual application load indices are listed.
The maximum weight (load carrying capacity) is also stamped on the lower sidewall of the tire. A driver should never exceed the maximum limits on the tire or the rim/wheel. Driving on an overloaded tire is hazardous. When a car is carrying too much, the weight can create excessive heat in the tire, which can cause sudden tire failure.
The speed symbol is a letter that indicates the speed category at which the tire can carry a load corresponding to its load index under specified service conditions. Speed ratings are based on laboratory tests that relate to performance on the road, but are not applicable if tires are underinflated, overloaded, worn out, damaged, or altered. In the example, the speed symbol “T” in the service description means a speed category of 118 miles per hour (or 190 km/h).
Excessive speed is not only unlawful but may also cause injury. Although a tire may be speed rated, Cooper does not endorse the operation of any vehicle in an unsafe or unlawful manner.
The most common speed ratings on passenger car and pickup truck tires are:
Q ….99 mph / 160km/h R …106 mph / 170km/h
S …112 mph / 180km/h T…118 mph / 190km/h
H …130 mph / 210km/h V…149 mph / 240km/h
W…168 mph / 270km/h Y …186 mph / 300km/h
Z …149+ mph / 240+km/h
Radial is the most popular type of tire and denotes a particular design in which the ply cords are arranged at 90 degrees to the direction of travel. Radial tires provide reliability, comfort, protection, stability, durability and maneuverability for drivers. A tire with radial construction will have the word “RADIAL” on the sidewall.
A radial tire is also delineated by the character “R” in the size designation.
DOT TIRE IDENTIFICATION NUMBER
The “DOT” symbol certifies the tire manufacturer’s compliance with U.S. Department of Transportation (U.S. DOT) tire safety performance standards. Next to these letters is the tire identification number (TIN), also known as the tire “serial” number.
Think of a tire’s identification number as its “birthday.” The first two digits are the factory code indicating where the tire was made. The last four digits identify the week and year of manufacture (Example: “0309” means third week of the year 2009), so drivers can know exactly when their tires were manufactured. Other characters in between the first four and last four characters are optional manufacturer’s codes for tire type, make, etc. All tires produced after September 2009 must have the full TIN on the intended outboard side of the tire and at least a partial TIN on the intended inboard side. The partial TIN does not include the date code.
It is important to know the DOT tire identification number in the event a driver needs to verify safety certifications or in the event of a manufacturer’s recall.
ADDITIONAL OPTIONAL SUFFIX LETTERS
- LT – Light truck
- ST – Special trailer
- TR – Tires for service on trucks, buses or other heavy vehicles. This suffix is intended to differentiate between truck tires and light vehicle tires with similar size designations.
- ML – Mining and logging tires used in intermittent highway service
- MH – Tires for mobile homes
- HC – Identifies a 17.5 rim diameter code tire for use on low platform trailers
- NHS – Not for highway service
- P – Indicates a P Metric tire
For more information on tire sidewalls as well as other important tire information, visit the Cooper Tire website here, and also see the Care and Service of Passenger and Light Truck Tires document on the U.S. Tire Manufacturers Association website.
Andrea Berryman / Director – Product Management
Andrea Berryman is the Director – Product Management for Cooper Tire & Rubber Company. In her role, Andrea leads the North America product development team to drive forward Cooper’s long term product strategy. Andrea’s efforts focus on Cooper brand products as well as Mastercraft, Starfire and private label brands.
Andrea joined Cooper in April 2017 as Product Manager – SUV. In January 2020, she was promoted to the role of Director – Product Management. Prior to joining Cooper, Andrea worked for the Dana Corporation where she was a Program Manager for commercial vehicles. Earlier in her career, she spent 24 years at Goodyear Tire & Rubber Company working in a variety of engineering and product marketing roles.
She holds a Bachelor of Science degree in chemical engineering from Purdue University and an MBA from the University of Kansas.