To draw the central part of the crossing member into the space between the dual tire treads and reduce abrasion by providing a core surrounded by a spiral spring and using a central member having elasticity and dimensional stability.

A crossing member 16 is maintained in an appropriate tension state on both treads of the dual tire through cooperation of an elastic tensioner 48 and a central member 50. The central member 50 is floated to move circumferentially during driving of the vehicle, drawing the chain into the space between tires of the dual tire. The central member is moved at a lower ratio than rotation of the tire. This prevents the central member from continuously drawing to twist and bend a specific crossing member. Otherwise, a desired uniform zig-zag pattern of the crossing member 16 on the dual tire may be distorted. The floating central member 50 reduces damages of the crossing member 16 at a place where the crossing member 16 comes into contact with the central member 50. Accordingly, the entire tire chain moves circumferentially during driving of the vehicle, thus reducing abrasion.