Brompton Transmission

The stuff which (with your help) drives your Brompton forwards .... Pedals, cranks, chainsets, chains, bottom brackets, chain tensioners and rear sprockets and spacers.

This includes the now famous (as of September 2017) Bottom Bracket (recalled due to a defect affecting up to 0.02% of Bromptons).

Here you can find, chains and chain tensions / ...

The stuff which (with your help) drives your Brompton forwards .... Pedals, cranks, chainsets, chains, bottom brackets, chain tensioners and rear sprockets and spacers.

This includes the now famous (as of September 2017) Bottom Bracket (recalled due to a defect affecting up to 0.02% of Bromptons).

Here you can find, chains and chain tensions / derailleurs, pedals, sprocket sets and crank sets / chain rings.   

More Info

Brompton Transmission We have 48 products.

Subcategories

  • Brompton Bottom Brackets

    Brompton Bottom Bracket

    The bottom bracket is a bit of an unsung hero in the bike world - it sits inside the bike frame (screwed in) and then has the pedal cranks bolted onto it or crank arms / spindle pushed through it

    (Brompton obviously recognise the importance as their code for the bottom bracket is Q100001 - i.e. part no 1 on the bike!)

    Every turn of the pedal rotates the spindle inside, keeping both cranks / pedals turning together - it has bearings inside which keep it moving smoothly (until they wear out)

    Which bottom bracket?

    Older / A Line / C Line / P Line

    The traditional Brompton (or A Line / C Line / P Line) use a sealed bottom bracket (i.e. no replaceable parts inside) with a square taper crank fitting (older cranksets use a ISO fitting and newer spider cranksets use a JIS fitting)

    These Bromptons use a 119mm length spindle and a 68mm shell

    It is possible to change to other styles of bottom bracket

    T Line

    With the introduction of the T Line came a different style of bottom bracket with external replaceable bearings 

    This bottom bracket (made for Brompton by FSA) can be retro-fitted to any Brompton - but also needs the new superlight crankset

  • Brompton chain tensioners

    The Brompton chain tensioner keeps the chain taught (so that the chain doesn't fall off of the bike when folding), and acts as a derailleur on Bromptons with two rear sprockets.

  • Brompton Chains

    Replacement chains for your Brompton

    Current Brompton folding bikes use two different specs of chains:

    We made a short video on A / C Line chain length calculation

    Q: What length Chain do I need for my Brompton C Line or A Line?

    A: The chain length for a Brompton C line can be worked out based on the number of teeth on the front chain ring and the number of teeth on the largest rear sprocket - as shown in the table below (or watching the video even further down)

    Largest Rear SprocketChain requiredChainring sizeNote
    12T/13T/14TQCHAIN096DR44TReduced gearing 3 speed / single speed
    15T/16TQCHAIN098DR44TReduced gearing 6 speed
    13TQCHAIN096DR46TVery old original chain ring (probably worn out)
    12T/13T/14TQCHAIN098DR50TStandard 3 speed Brompton
    16TQCHAIN100DR50TStandard 6 speed/Reduced gearing 2 speed
    12T/13T/14TQCHAIN100DR54TIncreased gearing 3 speed
    15/16TQCHAIN102DR54TStandard 2 speed/Increased gearing 6 speed

    The Brompton chain for A Line / C Line comes with a PowerLink to make chain removal and installation easy

    • We (and Brompton) recommend changing the rear sprocket(s) whenever the chain is changed / replaced (as they tend to wear together, so if you change just the chain, you may well find that the chain slips on the old sprocket when under load)

    All current Brompton bicycles use a 3/32 inch 8-speed chain (made for Brompton by SRAM) - Previously these 3/32 inch chains were only used on derailleur (2 and 6 speed) Brompton bikes

    Q: What length Chain do I need for my Brompton P Line or T Line (and C Line Electric)?

    A: The P Line / T Line (and now Brompton Electric P Line - 4 speed) comes with a choice of the following chains:

    • Brompton SL Advance 102 Links
    • Brompton SL Advance 104 Links 
    • Brompton SL Advance 106 Links

    These are 10 speed chains

    Please check the following table for the correct chain lengths

    Chainring sizeGearing Chain length
    564 Speed106 link 
    54 4 Speed104 link
    54 and 561 speed102 link 
    504 Speed102 link
    501 speed98 link

    We made the short video below to show how to:

    • Choose the correct chain length / size
    • Remove an existing Brompton chain
    • Install a new chain on your Brompton
  • Brompton Chainsets

    Brompton chainsets (cranksets), chainrings, guards and cranks

    Replacement / upgrade Brompton bicycle chainsets / chainwheel guards and crank arms

    The chainset (or crankset in US terminology) refers to the components of the bicycle which with the pedals drive the bike forwards

    The Brompton chainset does not include the bottom bracket - that is supplier separately

    Early Brompton bicycles used a fixed chainset where the crank arms were permanently attached to the chainring - so if you wanted to upgrade / change gearing - the whole component required changing. Very early models had a 40T chainring

    In 2013 a new spider crankset was introduced - this allowed the chain ring to be changed if it was worn or if a gearing change was required

    In 2015 the new spider crankset was made available as an upgrade to older bikes

    In 2016 the older fixed crankset was discontinued

    Brompton bikes now come with a choice of 3 chainring sizes: 44T, 50T and 54T (44T gives the lowest - easiest peddling - gearing, and 54T gives the highest - highest attainable speed - gearing)

  • Brompton Pedals

    Brompton bicycle pedals

    Brompton bikes use a standard pedal thread - that is 9/16inch diameter x 20 tpi (threads per inch) - so in theory you can use SPD's, MTB flats or stick with the Brompton ones

    The Brompton branded pedals are neat because the left hand one folds - so makes the bike more compact when folded and the non-folding right hand one matches it (and has the Brompton logo on the spindle) 

    We also like the MKS pedals - they have a folding solution and a quick removal solution - so you can still fold the Brompton to its smallest size

  • Brompton rear...

    Brompton sprockets and spacers

    Brompton sprockets (or cogs) for the range of  rear wheels used on Brompton folding bicycles past and present

    These wheels include the following:

    Brompton single/two speed rear wheel (uses a Shimano spline fitting)
    Brompton Sturmey Archer BSR (Brompton Standard Ratio) 3 speed rear wheel (uses a 3 spline ISO fitting)
    Brompton Sturmey Archer BWR (Brompton Wide Ratio) 6 speed rear wheel (uses a Shimano spline fitting)
    SACHS/SRAM 3 and 6 speed hub geared rear wheel (uses a 3 spline ISO fitting)

    Note: In 2017 Brompton have discontinued spare parts for the SACHS/SRAM 3 and 6 speed rear wheels. 

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Showing 1 - 12 of 48 items
Showing 1 - 12 of 48 items