Brompton Chain Tensioner Assembly

This tensioner is compatible with Brompton bicycles featuring a 2-speed internal gear hub, 6-speed SRAM, or 6-speed Sturmey Archer/BWR systems.

You can identify it by its two identical black jockey wheels that have a groove for the chain to sit in. The part code is QCTADR and the part number is 9023011.

It serves two main functions: keeping the chain at the correct tension while riding and during folding, and acting as part of the derailleur mechanism by allowing the chain to move between rear sprockets.

No, this tensioner is designed specifically for the 2-speed and 6-speed derailleur systems and is not compatible with single-speed Bromptons.

While installation can be done with standard bicycle tools, precise alignment is crucial. It is recommended to have it installed by a qualified bicycle mechanic to ensure optimal performance.

Regular cleaning of the jockey wheels and the tensioner assembly with a soft brush or cloth is recommended. Avoid using strong solvents.

A loose chain can be caused by incorrect tensioner adjustment, a worn chain, or improper installation. Check the tensioner's condition and alignment, and ensure the chain is the correct length for your Brompton setup.

Ensure the tensioner is correctly installed and aligned with the frame. Verify compatibility with your specific Brompton gearing system. If issues persist, consult a professional mechanic.

Check that the jockey wheels are clean and free of debris. Ensure the derailleur hanger is straight and the tensioner is not bent. If the problem continues, the derailleur cable may need adjustment.

Confirm that the chain is the correct length and that the tensioner is functioning properly, allowing for adequate slack. Check for any obstructions preventing the tensioner from moving freely.