The invention relates to a device which is used to free a vehicle that has become stuck in terrain or to reduce the risk of same, through the use of an additional tread which is disposed parallel to that of each wheel of the vehicle. The additional tread can take the form of an air chamber (2 or 10a and 10b) which may or may not be covered with a tire (11) or of a band comprising different coupling profiles (13, 14 or 15). Said tread is mounted to an anti-sink rim essentially comprising a conical profile (1.2) and a flange (1.1) which is centered in relation to, and applied against the outer side of the rim of the vehicle wheel using at least three bolts having special heads (6), which are inserted and coupled in respective openings in the flange and rim. The diameter of the system is smaller than that of the wheel in order to facilitate mounting and to reduce the risk of interference with the body of the vehicle. The conical shape of the rim profile (1.2) lends natural stiffness to the system and, when not in use, enables same to be easily stacked in order to minimize the storage space required.