Derailleur gears Derailleur gears Derailleur gears are a variable-ratio transmission system commonly used on bicycles, consisting of a chain, multiple sprockets of different sizes, and a mechanism to move the chain from one sprocket to another. Although referred to as "gears" in the bike world, these bicycle "gears" are technically "sprockets" since they drive or are driven by a chain, and are not driven by one another. Modern front and rear derailleurs typically consist of a moveable chain-guide that is operated remotely by a Bowden cable attached to a shifter mounted on the down tube, handlebar stem, or handlebar. When a rider
Derailleur gears cable-operated parallelogram rear derailleurs. In 1964, Suntour invented the "slant-parallelogram" rear derailleur, which let the jockey pulley maintain a more constant distance from the different sized sprockets, resulting in easier shifting. Once the patents expired, other manufacturers adopted this design, at least for their better models, and the "slant parallelogram" remains the current rear derailleur pattern. Before the 1990s many manufacturers made derailleurs, including Simplex, Huret, Galli, Mavic, Gipiemme, Zeus, Suntour, and Shimano. However, the successful introduction and promotion of indexed shifting by Shimano in 1985 required a compatible system of shift levers, derailleur, sprockets, chainrings, chain, shift cable, and