Brompton Transmission We have 48 products.

Subcategories

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  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

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  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.

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  Brompton Chains

  Replacement chains for your Brompton

  Current Brompton folding bikes use two different specs of chains:

  • The Brompton A Line / C Line use an 8 speed chain
  • The Brompton P Line / T Line and Electric C Line (4 speed - 2023 on) use a 10 speed chain

  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 Sprocket	Chain required	Chainring size	Note
  12T/13T/14T	QCHAIN096DR	44T	Reduced gearing 3 speed / single speed
  15T/16T	QCHAIN098DR	44T	Reduced gearing 6 speed
  13T	QCHAIN096DR	46T	Very old original chain ring (probably worn out)
  12T/13T/14T	QCHAIN098DR	50T	Standard 3 speed Brompton
  16T	QCHAIN100DR	50T	Standard 6 speed/Reduced gearing 2 speed
  12T/13T/14T	QCHAIN100DR	54T	Increased gearing 3 speed
  15/16T	QCHAIN102DR	54T	Standard 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 size	Gearing	Chain length
  56	4 Speed	106 link
  54	4 Speed	104 link
  54 and 56	1 speed	102 link
  50	4 Speed	102 link
  50	1 speed	98 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
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  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)

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  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

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  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.