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Brompton chain tensioner assembly for bikes with a derailleur - QCTADR



Replacement chain tensioner assembly for Brompton bicycles with a derailleur (2 speed or 6 speed)

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Brompton derailleur chain tensioner

Chain tensioner for 2 and 6 speed Brompton folding bikes

This chain tensioner is for Brompton folding bikes with 2 speed, 6 speed SRAM or 6 speed Sturmey Archer / BWR (Brompton Wide Ratio) gears

This can be identified by the fact it has 2 identical looking black jockey wheels where the chain sits in a groove in the jockey wheel

This works as a chain tensioner (keeping the chain tight when riding and folded) and as part of the Brompton designed derailleur mechanism - by having juckey wheels which can move from side to side to allow the chain to move between the two rear sprockets

To make your chain tensioner last as longer - keep your chain clean and not over lubricated

For details of how to adjust the Brompton derailleur, check out this technical video from Brompton.

Fitting instructions are included or can be viewed in the downloads tab

Brompton Q part code: QCTADR
Brompton part number: 9023011 

If you have a single, three or five speed Brompton (i.e. no derailleur) then you need the standard chain tensioner (QCTA)

We made this short video to help identify which chain tensioner you have, as well as how to remove and install it

We also made this video about how the chain tensioner fits into the Brompton derailleur system and how to adjust that

Have a question?

5 Question(s) answered - see below

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    Answered questions

  • Asked by Aoete Jr Apelu
    on 03/06/2019
    I would like to order the above part for my bike but im from Samoa and I don't even have a credit can I pay for it. Answer:
    Unfortunately we don't ship to Samoa due to our agreement with Brompton
  • Asked by Peter
    on 29/07/2019
    Hello. I have a Sturmey Archer fitted Brompton and want to eventually replace the cogs (13 and 16 tooth). Are these available from any Sturmey Archer service provider or does Brompton have a custom "Brompton-Sturmey-Archer" hub?Thank you ... Answer:
    Brompton uses a special hub on its 6 speed bike which allows two sprockets to be fitted - this is the BWR hub and uses Shimano style splines. The 3 speed - the BSR hub - uses ISO / 3 splines. Unfortunately the two are not compatible with each other. If you have a 6 speed already - then the Brompton 6 speed sprocket set will fit.
  • Asked by Tom Atkinson
    on 04/07/2021
    Is it okay to put some locktite on the thread that the chain tensioner nut screws onto? I adjust it to finger tight and then an extra 1/4 turn with the 15mm spanner but it is either too tight and there is resistance when turning the pedal or if I release it a little after a days riding the nut begins to unscrew itself. Answer:
    It should not need locktight and we would not recommend this. If you would like a. Idea for reference we made a while ago, link as follows:
  • Asked by David Glover
    on 23/12/2021
    Will this chain tensioner fit an old Brompton with a five speed hub and single rear sprocket? Answer:
    It is not suitable, you will need a Brompton chain tensioner assembly for bikes WITHOUT a derailleur, Reference: QCTA, link as follows:
  • Asked by Mark Wilkinson
    on 20/01/2022
    Is this suitable for an electric brompton too? Answer:
    Yes this is suitable for the 2 or 6 speed Brompton electric as well as the manual Brompton

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Chain tensioner assembly

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Data sheet

Comm Code87149990