Auto speed limiting safety installation for bicycle

The utility model relates to an automatic limiting speed safety device of a bicycle, which comprises a wheel rim, a bearing, a spoke and a bicycle frame, wherein a cylindrical tube is fixed on the spoke, a metal ball is stored in the cylindrical tube, elastic braking rubber is adhered on the lower surface of the bicycle frame, and the rubber is connected with the metal ball through a pulling wire. Baffle plates are respectively arranged in the cylindrical tube near both ends, and the maximum length of the pulling wire is less than the farthest distance between the elastic braking rubber and the wheel rim. The metal ball which is arranged in the cylindrical tube which is fixed on the spoke is outwards moved by the centrifugal action after the wheel rim is rotated, and the centrifugal force is bigger and bigger as the increase of the rotary speed of the wheel rim, since the metal ball is connected with the pulling wire of the braking rubber, and therefore, when the centrifugal force of the metal ball is bigger, the braking rubber can be driven to be inwards bent, which is finally leaned on the outer surface of the wheel rim to form bigger friction force and lower the rotary speed of the wheel rim. The utility model has the advantages of reasonable structure, wide application, special function, simple technique and the like.