How To Know a Real Winter Tire From a Multi-Purpose Tire

What's the difference in snow traction between an M+S (Mud and Snow) branded tire, an All-Season tire and a purpose-built winter tire? While many drivers probably aren't absolutely sure, it can be the difference between getting to work, getting home or getting stuck.

The original definition of M+S tires is based on the geometry of the tread design. The M+S designation was first used to differentiate the knobby bias ply tires intended for use on muddy, and/or snow-covered roads from the straight rib tires used on early cars or trucks. Tires with tread designs that meet the definition may be branded with the letters "M" and "S" in several different ways (e.g., M&S, M+S, M/S, MS, etc.) at the discretion of the tire manufacturer.

When early radial ply tires were also found to deliver more snow traction than the straight rib, bias ply tires, the tire companies introduced "All-Season tires." Supported by advertising, All-Season tires have presented an unspoken promise that they, throughout their life, can provide traction for all seasons...through spring's rain, summer's heat, fall's cooling and winter's snow. While this combined offering has made All-Season tires popular, many drivers have learned that a geometric definition doesn't guarantee winter snow and ice traction.

In 1999, The U.S. Rubber Manufacturers Association (RMA) and the Rubber Association of Canada (RAC) agreed on a performance based standard to identify passenger and light truck tires that attain a traction index equal to, or greater than 110 (compared to a reference tire which is rated 100) during the specified American Society for Testing and Materials traction tests on packed snow. The new standard helps ensure that drivers can easily identify tires that provide a higher level of snow traction.

A snowflake-on-the-mountain symbol branded on the tire's sidewall identifies tires that met the required performance in snow testing. The snowflake-on-the-mountain symbol was expected to be fully implemented on new tires by now. There are still some winter tires in the marketplace that meet the requirements to display the snowflake-on-the-mountain symbol but the molds used to make the tires were produced before the symbol was developed.