Q Celsius tires contain retractable studs for icy roads that are deployable via remote control. Manufacturers Qtires (reference to Q from James Bond?) have posted an animated video showing how the tires apparently work. From the FAQ:
The technology enables air pressure from the main chamber of the tire to expand a secondary chamber, which lifts the studs above the surface of the tread. When road conditions no longer require studs, the air pressure is released to atmosphere and the studs retract below the tread face.
Link (via New Scientist)
