Understanding Tire Code: Load Index, Speed Rating, and M+S Designation

The uniform tire code is imprinted on nearly every vehicle tire manufactured. This code not only identifies the tire, it also provides useful information about the tire. The first post focused on the type of tire and section width and the second post looked at aspect ratio, tire construction and wheel diameter. With this post, we complete our look at tire code with an explanation of the last three parts of the uniform tire code: load index, speed rating, and M + S designation.

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Tire Code – Performance┬áIndex, Speed Rating, and Mud and Snow Designation

Performance Index
The tire performance index is displayed after the wheel diameter, and represents the tire’s load and speed ratings. In this case, the 93 load index represents 1,433 pounds, and the speed rating of V represents 149 mph.

Common Speed Ratings

Letter

L

M

N

P

Q

R

S

T

U

H

V

Max. MPH

75

81

87

93

99

106

112

118

124

130

149

All-Season Tires with Mud and Snow Designation
When a tire has M+S on it, that means that it meets the Rubber Manufacturers Association (RMA) guidelines for a mud and snow tire. Similar markings for this include MS, M&S, and M/S. In order for a tire to receive the Mud and Snow designation, it must meet specific RMA geometric requirements.

A tire with the correct tire load index for your vehicle means you that your tires are made to handle the weight of your vehicle. The speed rating shows the maximum speed your tires can handle, which tends to be more important in countries with roadways that are not subject to speed limitations. Whether or not the mud and snow designation is important will depend on the climate in which you live and drive.

Along with looking at the tire code, it is important to follow your vehicle manufacturer’s recommended specifications to assure safety and best vehicle performance. Selecting a dependable, quality tire is just the beginning. Maintaining the proper tire pressure will help you extend the life of your tires .