PURPOSE: To prevent the tumble of a car body to the utmost during its turning by moving wheels in the direction stably supporting the car body against the ground in defiance of the tumbling force of the car body.

CONSTITUTION: The driving force from an engine 3 is fed to a transmission 5 fitted to the lower section of a front car body frame 14 through a clutch, and it is conveyed to the right and left front wheels 6, the rotary axis P2 of which is located near the rear end of the frame 14, through an axle case 17 from a front wheel differential mechanism 16. During the turning of the car body, the front wheels 6 are positioned in the rear of the up-and-down sway axis P1 of a front car body 7 and a rear car body 11 so that the front wheels 6 are largely stretched outward from the turning locus of the rear wheels 10 when both car bodies are swayed relatively to each other during the turning of the car body.