0 a type of bicycle gear that works by moving the bicycle chain from one sprocket wheel (= a wheel with a row of tooth-like parts) to another -- （自行车的）换挡装置，变速器
Its products ranged from suspension forks to derailleurs.
Shifter controls are mounted so that the right shifter controls the rear derailleur and the left shifter controls the front derailleur.
Though they are heavier than comparable derailleur systems, internal-gear hub systems generally last longer and require less maintenance.
His victory was controversial as he was the first rider to complete the race using a modern derailleur.
This requires a sprung chain tensioner, similar to a rear derailleur, to be used.
The others had derailleur gears for a higher ratio for the sprint.
A hub gear system provides greater ease-of-use and safety than a derailleur system, can provide a wide range of ratios, and requires little maintenance.
Meeting both these requirements is only possible if the rear derailleur is compatible with the gear range being used on the bike.
