Tire Code Part 3: Load Index, Speed Rating, and M+S Designation

When shopping for tires, you can learn a lot about a particular tire by looking at the uniform tire code imprinted on the tire. This code not only identifies the tire, it also provides useful information about the tire. Previously we looked at type of tire and section width, next we discussed at aspect ratio, tire construction and wheel diameter. With this post, we complete our series with a look at last three parts of the uniform tire code: load index, speed rating, and M + S designation.

Performance Index
The tire performance index is displayed after the wheel diameter, and represents the tire’s load and speed ratings.

Common Speed Ratings

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.

Once you’ve purchased your new tires, 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 .