In the snow:

• Tread lug under load sinks into the snow
• Tread lug deformation, penetration of edges: "GRIP" with low slip
• Shearing-off effect in snow: "SLIDING" with high slip

Even ground compacts the snow

Tilted edges produce pressure peak, which result in further penetration into the snow

Sliding of rubber on snow and snow on snow

On ice:

• Tread lug deformation as traction builds up "GRIP"
• As they "SLIDE", they create frictional heat which melts the surface of the ice

Generation of pressure peaks at the edge of the sipes, edges do not lift off as they leave contact area.

By distorting the film of water (windscreen wiper effect), the sipes increase the tractive force.