Winter Tires
The evolution of
winter tires EVEN THE 3-PEAK MOUNTAIN SNOWFLAKE ISN’T ENOUGH ANYMORE By
Bob Ulrich
T
rue or false: A tire with the 3-Peak Mountain Snowflake symbol stamped on the sidewall is always a winter tire. The answer is false: A winter tire must be branded with the symbol, but that alone doesn’t make it a winter tire. True or false: The 3-Peak Mountain Snowflake symbol is a better indication of winter performance than the M+S designation. The answer is true: The 3-Peak Mountain Snowflake symbol is a performance standard, while the M&S designation is a visual standard. To better understand these answers is the first step in defining a winter tire.
MUD + SNOW The M&S designation developed in the 1970s as a way of distinguishing tires with aggressive tread patterns from bias-ply tires
CANADIAN PASSENGER TIRE UNITS SHIPPED 2004-2018 (in millions) Year 2018 2017 2016 2015 2014 2013 2012 2011 2010 2009 2008 2007 2006 2005 2004
Overall 20.0 18.4 18.4 18.8 18.0 15.8 15.6 16.0 16.5 20.0 19.0 17.4 16.4 17.6 16.7
Winter 8.0 7.2 6.6 7.2 7.0 4.6 4.8 4.9 5.3 7.5 7.0 5.5 5.3 6.0 5.3
SOURCES: TIRE AND RUBBER ASSOCIATION OF CANADA, MODERN TIRE DEALER
20
%winter 40.0% 39.1% 35.8% 38.3% 38.9% 29.1% 30.7% 30.6% 32.1% 37.5% 36.8% 31.6% 32.3% 34.1% 31.7%
with the more traditional ribbed patterns, according to Woody Rogers, tire information specialist at The Tire Rack Inc. “At the time, aggressive tread is where they achieved better… traction,” he said. “Of course, they changed the compounding a little bit, too. “But M+S isn’t a performance standard. It is merely a visual standard. The tread pattern has to have at least 25% open space from a two-dimensional standpoint. And it has to have a ½-inch notch in one shoulder… every so often. “That’s it. You could take a 1965 bias rib tire, open it up just a little bit, put a notch in one shoulder, and that is an M+S tire. It has nothing to do with how much traction it actually has in the mud or on snow.” Here is the Tire Information Service Bulletin (Vol. 10, No. 7) that defines snow tire definitions for passenger and light truck tires, courtesy of the U.S. Tire Manufacturers Association (USTMA): Passenger and light truck tires meeting the following criteria are marked on at least one sidewall with the letters “M” and “S” (e.g., MS, M/S, M&S, M+S, etc.). These tires have been designed to provide better starting, stopping, and driving performance in snow conditions than non-M&S tires, and have the following general characteristics: 1.
The new tire tread shall have multiple pockets or slots in at least one tread edge that meet the following requirements based on mold dimensions:
a.
Extend toward the tread center at least 1/2 inch from the footprint edge, measured perpendicularly to the tread centerline.
b.
A mimimum cross-sectional width of 1/16 inch.
c.
2.
Edges of pockets or slots at angles between 35 and 90 degrees from the direction of travel.
The new tire tread contact surface void area will be a minimum of 25% based on mold dimensions. (USTMA)
In 1999 USTMA (formerly the Rubber Manufacturers Association) and Rubber Association of Canada (RAC) jointly defined tires for use in severe snow conditions.
3-PEAK MOUNTAIN SNOWFLAKE The mountain snowflake symbol doesn’t replace the M+S designation, it just adds to it. Here is the Tire Information Service Bulletin (Vol 37, No. 5) that defines passenger and light truck tires for use in severe snow conditions: • Tires designed for use in severe snow conditions generally have tread patterns, structure, and materials to give superior performance in snow over tires meeting the USTMA Snow Tire Definition. • Tires designed for use in severe snow conditions are recognized by manufacturers to attain a traction index equal to or greater than 110 (Snow Grip Index of 1.10) compared to the ASTM E1136 Standard Reference Test Tire when using ASTM F1805-06 snow traction test with medium packed snow surface and equivalent percentage loads. Other test methods and reference tires developed by standardizing bodies may be used provided proper correlations are demonstrated. • Tires designed for use in severe snow conditions that meet the performance criteria above qualify for marking on at MTD March 2019
