Severe Service Emblem
You may have noticed on our web site “the snow flake on the mountain peak” symbol on all Nokian winter tyres. There are a lot of different terms used today in the tyre industry. Some of them actually mean something and some do not. The following helps explain why it is required and some history.
High speed rated, high performance summer tyres
If your tyres are marked with a V, ZR, W or Y speed rating they are high performance “summer” road tyres and were never designed for driving on snow covered roads. High speed rated summer tyres, by definition are not winter/snow tyres. All high performance AWD summer tyres become like hard plastic when the temperature falls below 7° thereby losing the flexibility needed to build up sufficient grip for braking, for starting traction and for cornering.
Today’s tyre tread designs and compounds maximize long, even wear… not winter traction.
All season tyres
Then when radial ply tyres were also found to deliver more snow traction than the straight rib bias ply tyres, the tyre company marketing departments saw an opportunity, and the term “all-season tyre” was born. Supported by advertising, all-season tyres have presented an unspoken promise that they, throughout their life, can provide traction for all-seasons…through spring’s rain, summer’s heat, autumn’s cooling and winter’s snow. And while this combined offering made all-season tyres popular, the problem is that this geometric definition doesn’t guarantee performance or any degree of safety in winter driving.
Off-road and all-terrain AWD tyres
Off-road and all-terrain AWD tyres are not specifically designed for winter/snow driving either. These types of AWD tyres are designed for off-road driving on gravel, sand and rocks and have a very high noise level. Under cool conditions—not just cold or freezing conditions—the rubber in these tyres gets even harder.
This stiffer tread compound does not conform to irregular road texture as well, and as a result has less actual contact with the road surface. Because off-road tyres have very limited siping on their tread they provide little traction in icy conditions. Only severe service winter tire has the compound to remain soft and pliable at lower temperatures.
M+S marking on tyres is very misleading.
Many AWD tyres are rated M+S, M&S or M/S, i.e., mud and snow. Established by the USA Rubber Manufacturers Association (RMA), the M+S designation refers only to the tread pattern. The M+S standard calls for a tyre with grooves at the outside of the tread that extend into the centre. It also means that 25% of the tyre tread contact surface be open, i.e., a more open tread pattern.
You will find the M+S symbol on most all-season tyres, on off-road and all-terrain tyres and even some high performance summer tyres may have this designation. However, there are no performance standards to meet or traction tests to pass. Any tyre with grooves at angles and with 25% of the tread void can be labelled as M+S.
And on icy snow and on ice, the open tread grooves have zero effect on performance. Control of the vehicle comes strictly from equal parts of the tyre rubber compound that provides adhesion and the effects from the tread sipes.
In 1999, the RMA defined a real “snow” or winter tyre with its severe snow-rating. Car and AWD tyres that pass this performance test and are embossed with the “snowflake on a mountain peak” icon. Severe snow-rated tyres must provide traction at least 10% better than a standard reference test tyre.
The off-road, all-terrain and all-season M+S tyres cannot pass this test. The M+S rating doesn’t mean much. The severe snow rating does.
Severe Service Winter/Snow Tyres
All Nokian Tyres have the snowflake-on-the-mountain symbol denoting that they are suitable for use in severe snow conditions. The snowflake-on-the-mountain-peak symbol indicates a severe snow service conditions rating.
In order to meet this standard, tires must be tested using an American Society for Testing and Materials (ASTM) testing procedure described in “RMA Definition for Passenger and Light Truck Tires for use in Severe Snow Conditions”. Tires designed for use in severe snow conditions are recognized by manufacturers to attain a traction index equal to or greater than 110 compared to the ASTM E-1136 Standard Reference Test Tire when using the ASTM F-1805 snow traction test with equivalent percentage loads.
Tyres bearing this symbol will provide snow performance far superior to tyres only bearing the M+S symbol.
The safety of any AWD vehicle in snow and icy conditions is determined by the tyres. First and foremost, the single most important aspect of a winter tire is the tread compound that remains soft at lower temperatures. Always remember that no matter how many safety features an AWD vehicle has it is the tyres that determines how it drives and handles on snow and ice.