Maximum Load Rating; Maximum Permissible Inflation Pressure; Snow Tires- Page 562

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Customer Information and Reporting Safety Defects

Tire Information (U.S.A.)

M    S or M/S: Mud and Snow

AT: All Terrain.

AS: All Season. The “M S” or “M/S” indicates that the tire has some functional use in mud 

and snow.

U.S. DOT Tire Identification Number (TIN)

This begins with the letters “DOT” which indicates the tire meets all federal standards. The 

next two numbers or letters are the plant code where it was manufactured, and the last four 

numbers represent the week and year the tire was manufactured. For example, the numbers 

457 means the 45st week of 1997. After 2000 the numbers go to four digits. For example, 

the number 2102 means the 21th week of 2002. The other numbers are marketing codes 

used at the manufacturer's discretion. This information is used to contact consumers if a tire 

defect requires a recall.

Tire Ply Composition and Materials Used

The number of plies indicates the number of layers of rubber-coated fabric in the tire. 

In general, the greater the number of plies, the more weight a tire can support. Tire 

manufacturers also must indicate the tire materials, which include steel, nylon, polyester, 

and other.

Maximum Load Rating

This number indicates the maximum load in kilograms and pounds that can be carried by the 

tire.

Maximum Permissible Inflation Pressure

This number is the greatest amount of air pressure that should ever be put in the tire under 

normal driving conditions.

Tread Wear, Traction and Temperature Grades
Tread wear:

 The tread wear grade is a comparative rating based on the wear rate of the tire 

when tested under controlled conditions on a specified government test course. For example, 

a tire graded 150 would wear one and one-half (1 1/2) times as well on the government 

course as a tire graded 100.

Traction:

 The traction grades, from highest to lowest are AA, A, B, and C. The grades 

represent the tire's ability to stop on wet pavement as measured under controlled conditions 

on specified government test surfaces of asphalt and concrete. A tire marked C may have 

poor traction performance.

Temperature:

 The temperature grades are A (the highest), B and C, representing the 

tire's resistance to the generation of heat and its ability to dissipate heat when tested under 

controlled conditions on a specified indoor laboratory test wheel.

Snow Tires

In some heavy snow areas, local governments may require true snow tires, those with very 

deeply cut tread. These tires should only be used in pairs or placed on all four wheels. Make 

sure you purchase snow tires that are the same size and construction type as the other tires 

on your vehicle.

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