The rear derailleur is located on a bicycle with derailleur gears, which is attached to the frame by a derailleur hanger near the rear wheel axle. When pedaling, the chain runs over a chainring through the rear derailleur via a sprocket back to the chainring. When you operate the shift lever to jump from one sprocket to the next on the rear wheel, a gear change is initiated mechanically or electronically. The rear derailleur ensures that the running chain is also transferred to the next sprocket and consists roughly of a cage, a shifting parallelogram and two shifting or deflection pulleys.
