Derailleur gears by 13 drive-train. Most road bicycles have two chainrings, and touring bicycles commonly have three. The rear derailleur serves double duty: moving the chain between rear sprockets and taking up chain slack caused by moving to a smaller sprocket at the rear or a smaller chainring by the front derailleur. In order to accomplish this second task, it is positioned in the path of the bottom, slack portion of chain. Sometimes the rear-derailleurs are re-purposed as chain tensioners for single-speed bicycles that cannot adjust chain tension by a different method. Although variations exist, as noted below, most rear derailleurs have
Ascent of the A-Word the book as an "often raucously funny account of what seems to be America’s most popular insult" which manages to be neither "exceedingly snarky" nor "overly academic and pretentious". Ascent of the A-Word Ascent of the A-Word: Assholism, the First Sixty Years is a 2012 book by the American linguist Geoffrey Nunberg which analyzes the history of the epithet "asshole". In "Ascent", Nunberg traces to World War II the origins of the word as an epithet, when it was used as a term of abuse for superior officers considered abusive or self-important. Following the soldiers' return home from the war,