To make a ground-contact width against a road surface large even when the vehicle rides over the road surface with a stepped part and to enhance comfortability to ride.

Of the tires 2, a length dimension against a radial direction of an inner side wall 2B positioned at the inner side of the vehicle is set longer than that of an outer side wall 2C positioned at the outside the vehicle. An outer diameter of an inner bead seat part of a rim 4 is set smaller than an outer diameter of an outer bead seat part in responsive to the length dimension of the inner side wall 2B and the length dimension of the outer side wall 2C. Thereby, when the vehicle rides over the road surface with a stepped part, even if a wheel 1 integrated with an arm 7 is turned making a connection part 6A as a center and is largely inclined so as to fall down at the inside of the vehicle, the ground-contact width of the tire 2 is enlarged by largely elastically deforming the inner side wall 2B than the outer side wall 2C.