Abstract: A light weight bicycle frame has open section, e.g. I section, parts cast in a light weight metal or alloy, preferably a magnesium alloy. A frame consists of an upper bar, and a lower bar, a saddle stem, a head, and rear forks. The bars are of I section and the saddle stem is of U section merging into or taking a tubular section receiving a saddle support tube. A structural bridge of I section interconnects the bars. The lower bar joins the saddle stem at a point intermediate the ends thereof and above the bearing for a crank wheel.

Abstract: A bicycle frame includes a saddle stem (3) and a head (4) interconnected by upper (1) and lower (2) bars and integrally cast in a lightweight metal or alloy, particularly magnesium. At least the lower bar (2), and preferably also the saddle stem (3) is cast in an open section which is subsequently closed by means of a second casting (33,36) secured in the open section by adhesive and preferably also mechanically interlocked therewith. The mechanical interlocking is provided by interengaging elements (41, 42, 43) arranged at an angle oblique to the length of the castings. The upper (1) and lower (2) bars are joined by a structural bridge (31) linking them at a location between the head (94) and the saddle stem (3). The lower bar (2) joins the saddle stem (3) at an intermediate point.