Bicycle

A bicycle comprises a body frame which fixedly supports a saddle, and rotatably supports rear and front wheels to transmit a driving force to said front wheel by pedaling a pedal by foot, further comprises a large gear which can be rotated integrally with said rear wheel and is provided concentrically with said rear wheel about a rear wheel axle, and includes a diameter smaller than that of said rear wheel,

• a small gear which is provided so as to circumscribe said large gear at a level above the rear wheel axle,
• a small gear supporting bracket which is provided so as to swing about said rear wheel axle, and rotatably supports said small gear at its upper end, and includes a load receiving surface at its lower end,
• a load transmission unit which is downwardly movably supported to said body frame due to the downward load and adjustably movable in the longitudinal direction of the bicycle on said load receiving surface,
• a first sprocket which is provided concentrically with said small gear so as to be rotatable integrally with said small gear,
• a second sprocket which is rotatably provided at the position of the bicycle rear of said first sprocket and at the level lower than the rotation center of said first sprocket,
• a chain which is wound between said first and second sprockets to transmit the rotation force between said first and second sprockets, and
• a first rachet which is mounted on said small gear so as to restrict the rearward rotation of said rear wheel via said large gear,
• whereby the driving force can be transmitted to said rear wheel only by pedaling said pedal with said first rachet being disengaged from said small gear, while a physical burden on legs of a rider can be reduced by engaging said first rachet with said small gear to utilize the downward load, in accordance with the longitudinal position of said load receiving surface of said load transmission unit, in a case where the bicycle climbs an uphill slope.