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
English translations of Asterix "Why is that man wearing a melon?" This relies on the fact that the French word for melon is "also" the name for the iconic British bowler hat; with no way to convey this in the English translation, in the British edition Obelix says, "I say, Asterix, I think this bridge is falling down" referring to the children's rhyme "London bridge is falling down", leaving the original joke incomplete. In the panel shown, the reply of the British man on the right was "Rather, old fruit!", in some publications of the book; a good pun and typical of the way