Brompton Advance Rear Derailleur

Restore Crisp Shifting on Brompton Advance 4- and 12-Speed Bikes The Brompton Advance Rear Derailleur is the factory replacement mech for bikes using the Advance rear frame and 4 external gears. It handles the derailleur side of both 4-speed and 12-speed Brompton drivetrains, moving the chain cleanly across the sprockets so every gear clicks in where it should. Over time, impacts, corrosion, or simple wear can lead to vague shifts, chain noise, or misaligned gears. Swapping in a new Advance derailleur brings the system back to how it left the factory, especially when paired with a fresh cable and correctly set limit screws. Design That Works Direct replacement for the Advance derailleur used on Brompton bikes with 4 external gears on the Advance rear frame. Supports both 4-speed external-only setups and 12-speed systems that combine 4 derailleur gears with a 3-speed hub. Engineered for precise indexing with the dedicated 4-speed shifter, keeping shifts light and predictable. Supplied with fixing bolts and designed to mount directly to the Advance rear frame hanger using a 2 mm hex key. Best performance when kept clean and lightly lubricated at the pivots and jockey wheel bushings.