Snow has fallen and as a result the news was buzzing about snow tires. What constitutes a snow tire and who has to use them, and when? It seemed as if there was some disagreement between the RCMP and the Ministry of Transportation.
There has been a tire designation for quite some time that is simply M and S which I assumed all my life meant Mud and Snow. Correct me if I am wrong. If you are a tire sidewall reader you will find the M+S, MS, M&S M/S designation likely on both your summer and winter tires. It seems that any tire that you purchase that is not a super high performance or ultra high performance summer tire has this designation. It is the designation found not just on winter tires but also all season tires.
Originally the M&S was placed on bias ply tires that had a more blocky tread pattern that was significantly different than those that had only circumferential ribs. The blocky pattern obviously provided better traction in snow then the circumferential ribs. The radial ply tire then came along and quickly showed that it also provided better traction on snow than the old bias ply particularly when the tread pattern was blocky.
Then along came all season tires. The be all and the end all. One set of tires for all seasons. Maybe if you live in Southern California. In the Kootenays I would recommend a full blown snow tire.
As in all things “automotive” technology has not stood still. What constitutes a snow tire of yesteryear just would not cut it in this day and age. Today’s snow tires sport a mountain symbol with a snowflake in it on your tires’ sidewall. In 1999 the US Rubber Manufacturers Association (RMA) and the Rubber Association of Canada (RAC) agreed on a traction based standard. To receive this designation a tire would have to receive a traction value of 110 or greater in the ASTM (American Society of Testing Materials) F-1805 snow traction test. A tire with the mountain snowflake symbol on it has 10 per cent better traction on packed snow than the reference tire (an all season tire) – 10 per cent is the minimum.
There are tires that receive traction values of 130 and 140. That is 30 to 40 percent more traction. Impressive! There are now all season tires that meet the mountain snowflake symbol standard.
As in all things choosing a winter tire will involve some compromise. Your winter driving habits and the area you live in will determine your needs.
Winter tires are designed to stay soft at cold temperatures. The tread blocks are full of sipes that allow the tires to conform to the slightest surface roughness even on ice. They channel water out from under the tread.
They may have added materials like walnut shells or fibres the make them grip like sandpaper to smooth surfaces. The tread pattern is blockier for digging in and shedding soft snow.
Soft rubber means high speed driving on dry roads will wear your winters quickly. Soft rubber also means your sports car handling will suffer. Reaction to steering inputs will be slower as your contact with the road will squirm a little bit more. So when you are sporting your winter tires drive accordingly.
When looking closely at the B.C. snow tire rules you will actually see they are very lax. Simply consulting a professional and letting them help you choose a proper tire for our winter season will be the best approach. That extra winter traction is well worth the investment.
Trail’s Ron Nutini is a licensed automotive technician and graduate of mechanical engineering from UBC. E-mail: nutechauto@telus.net