PURPOSE: To make it possible for a car to travel on the usual paved road and the slippery road by arranging snow/ice crunching means capable of projecting by the introduction of fluid pressure and retracting by discharging the fluid pressure on the ground contact surface of a tire, and connecting the crunching means to pressure loading means.

CONSTITUTION: Peripheral grooves 3 are respectively formed near both sides of the ground contact surface 2 of a tread, and small-sized cylinders 4 are buried in the grooves at fixed intervals. The output shafts 5 of pistons are arranged on the outer ends of the small-sized cylinders 4, and air pressurizing pipes 6 are connected to the inner ends of the pistons. The two small-sized cylinders 4 are formed in sets, and the output ends 7 of the pistons of the cylinders 4 forming each set are connected to each other by chains 8. When air pressure is supplied to the respective small-sized cylinders 4 to project the pistons, the chains 8 are projected together with the pistons and tensed between the pistons to crunch snow/ice on the road surface. When the supply of air pressure is interrupted, the chains 8 are retracted along with the pistons, and sunk into the grooves 3 to release the slip preventing function.