Derailleur gears designed and built in the late 19th century. One example is the Protean two-speed derailleur available on the Whippet safety bicycle. The French bicycle tourist, writer and cycling promoter Paul de Vivie (1853–1930), who wrote under the name "Vélocio", invented a two speed rear derailleur in 1905 which he used on forays into the Alps. Some early designs used rods to move the chain onto various gears. 1928 saw the introduction of the "Super Champion Gear" (or "Osgear") from the company founded by champion cyclist Oscar Egg, as well as the Vittoria Margherita; both employed chainstay mounted 'paddles' and single
Derailleur gears = 45T; medium = 33T SRAM long = 43T; medium = 37T; short = 30T Benefits of a shorter cage length: There are at least two methods employed by rear derailleurs to maintain the appropriate gap between the upper jockey wheel and the rear sprockets as the derailleur moves between the large sprockets and the small sprockets. The actuation ratio is the ratio between the amount of shifter cable length and the amount of transverse derailleur travel that it generates. Shift ratio is the reciprocal of actuation ratio and is more easily expressed for derailleurs than actuation. There are currently