Winter tire, showing tread pattern designed to compact snow in the gaps. Such tires that have passed a specific winter traction performance test are entitled to display a “Three-Peak Mountain Snow Flake” symbol on their sidewalls. Some snow tires have metal or ceramic the jacket i wear in the snow pdf that protrude from the tire to increase traction on hard-packed snow or ice. Studs abrade dry pavement, causing dust and creating wear in the wheel path.
Regulations that require the use of snow tires or permit the use of studs vary by country in Asia and Europe, and by state or province in North America. The tread design of snow tires is adapted primarily to allow penetration of the snow into the tread, where it compacts and provides resistance against slippage. The snow strength developed by compaction depends on the properties of the snow, which depend on its temperature and water content—wetter, warmer snow compacts better than dry, colder snow up to a point where the snow is so wet that it lubricates the tire-road interface. New and powder snow have densities of 0. Compacted snow may have densities of 0. Snow or ice-covered roadways present lower braking and cornering friction, compared to dry conditions. The roadway friction properties of snow, in particular, are a function of temperature.