Long-travel rear suspension system for bicycles

An improved bicycle rear suspension system comprises a main frame (20) and a swingarm (22), the former having a seat (32) and the latter having a rear wheel (34) and a pedal crankset assembly (38) mounted on it. The suspension has predetermined proportions which provide long travel, or bump absorbing motion, without exhibiting pedaling-induced motion. The swingarm (22) is hinged to the main frame (20) at a single pivot axis (24). The specified location of the pivot axis is such that the suspension is several times firmer when the rider is standing than when the rider is sitting. This pivot location also ensures that the pedaling forces applied to the swingarm (22) are substantially balanced throughout the pedal stroke. This mechanism also provides a frame geometry which can adjust to different terrain conditions. A lightweight structure for the swingarm (22) provides high strength and stiffness. The swingarm (22), when viewed from the side, presents a diamond shape divided into a plurality of triangles. The forward vertex of the diamond is at the pivot axis, and the rearward vertex is at rear axle (52). The pedal crankset assembly (38) is mounted at the bottom vertex of the swingarm (22) and a shock absorber (36) is attached to the top. The swingarm (22) with a shock absorber (36) and a seat tube (66) forms a truss structure which provides high strength and stiffness, yet is lightweight and easy to manufacture.