NHTSA's alpine symbol for snow tires
All-season tires are a design compromise that allows you to maintain a basic level of both winter and summer performance, but don’t offer maximum performance in either season. They're like tennis shoes; you can wear them on the beach and in the snow, but flip flops on the beach and warm boots in the snow perform better in those conditions.
If you live on the fringe of the snow belt and drive in snow once or twice in a winter, then all-season tires will suffice as long as they are relatively new. But for those of us who live in the snow belt or who visit snowy areas on a regular basis, winter performance tires -- snow tires -- are the responsible choice.
The tread compounds and designs that make summer tires work so well in warm temperatures will severely limit their winter performance. A tire that performs brilliantly on high-temperature roadways typically has stiff sidewalls and a harder, shallower tread compound. This compound becomes even harder, almost like plastic, when exposed to lower winter temperatures. As you have probably seen, plastic sleds slide quite well on snow, and summer tires won’t do anything to help you drive safely in the snow.
A snow tire's of more-flexible sidewalls, winter tread patterns, deeper tread depth, and perhaps most importantly, tread compounds that remain soft in the lowest temperatures combine to make snow tires deliver maximum performance at winter temperatures and on ice, snow and slush.
Be wary, though: retailers offer a wide range of tires sold as “winter tires” with an “M&S” rating, but they are not at all equal in performance. Many are thinly disguised all-season tires or lower quality tire brands using outdated technology to give the impression that the tires are suitable for winter use.
The best performing winter tires have a mountain/snowflake symbol branded on the tire's sidewall. The RMA (Rubber Manufacturers Association) designates winter tires that meet the newest severe snow standard with this special symbol. This rating sets the true winter tire apart from other standard M&S rated all-season designs. Tires that have earned this symbol can be expected to provide twenty-five to fifty percent more traction in winter’s worst conditions, which may be easily the difference between driving safely and losing control in the snow and ice. In fact, winter tire technology has improved so dramatically in recent years that several states and provinces are considering requiring the use of winter-specific tires in designated areas to improve traffic safety.
Always install winter tires on your vehicle in sets of four, whether you have a rear, front or all-wheel vehicle. This is also true of summer tires. Using two different types of tires on your vehicle will negatively affect its handling, as the vehicle suspension will not be able to perform as originally designed. Vehicle manufacturers spend countless hours and millions of dollars to maximize both a car’s handling and the performance of its ABS and stability control systems. Why disrupt this balance by creating different levels of performance on each end of your car? Many tire dealers will not sell sets of two snow tires due to the potential liability of doing so. The goal here is to drive safely on snow and ice!