Snow tire

Snow tires—often also called winter tires—are tires designed for use in colder weather, snow and ice. Snow chains can be a slower-speed, temporary alternative in snowy conditions. Snow tires have a tread design with bigger gaps than those on summer tires, increasing traction on snow and mud. Some have metal studs to increase traction on ice. Tires designed for winter conditions are optimized to drive at temperatures below 7 °C (45 °F).

Studded tires with metal pins that protrude from the tire can greatly reduce skidding and accidents on snow or ice-covered roads. However, the metal studs make contact with the road pavement and eventually cut into the pavement, allowing water to get in. The water can cause road damage and create hydroplaning hazard.

Snow tires operate on a variety of surfaces, including pavement (wet or dry), mud, ice, or snow. 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 0.1 to 0.3 g/cm² (0.20 to 0.61 lb/sq ft). Compacted snow may have densities of 0.45 to 0.75 g/cm² (0.92 to 1.54 lb/sq ft).

The compacted snow develops strength against slippage along a shear plane parallel to the contact area of the tire on the ground. At the same time, the bottom of the tire treads compress the snow on which they are bearing, also creating friction. The process of compacting snow within the treads requires it to be expelled in time for the tread to compact snow anew on the next rotation. The compaction/contact process works both in the direction of travel for propulsion and braking, but also laterally for cornering.

The deeper the snow that the tire rolls through, the higher the resistance encountered by the tire, as it compacts the snow it encounters it to either side. At some point on a given angle of uphill pitch, this resistance becomes greater than the resistance to slippage achieved by the tread's contact with the snow and the tires with power begin to slip and spin. Deeper snow means that climbing a hill without spinning the powered wheels becomes more difficult. However, the plowing/compaction effect aids in braking to the extent that it creates rolling resistance.

...
Wikipedia