Always choose Winter Tires!!!
All Season tires are a design compromise. As good as they are in most conditions; All-season tires are not optimized for winter conditions in the same way that Severe Snow tires are optimized. Severe Snow tires have cold weather rubber compounds, channeling tread patterns, a large number of tread sipes for wet surface control, and an open tread block pattern for better deep snow traction.
All Season tires are not a substitute for Winter tires.Use a set of four, matched, winter tires for winter driving. Do not put just 2 on in hopes that it will work the same. This mismatch in tires between front and rear can cause unstable vehicle handling and should be avoided.
A study conducted by the Quebec Ministry of Transport showed a proper winter tire can improve braking by up to 25% over an all season radial and can improve collision avoidance by about 38%.
At the beginning of the winter, drivers should always ensure that the tires have grooves at least 4.8mm deep. The deeper the grooves, the better the tire's traction on a snow covered surface. On an icy surface, a winter tires softer rubber is the main factor allowing a good grip. Remember that winter tires retain their elasticity down to -40 degrees Celsius.
When the temperature drops below 7 degrees Celsius, All Season tires start to lose their elasticity, which results in poorer traction, handling and braking capacity. Winter tires, on the other hand, retain their elasticity at temperatures far below that. Also, it must not be forgotten that modern vehicles are equipped with safety features (ABS, electronic stability control, traction control, and so on) which work properly only if the vehicle is equipped with tires providing the proper adherence.