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.   

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Brompton Transmission We have 42 products.

Subcategories

  • Brompton Bottom...

    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

    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)

    Brompton 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)

    Brompton use a 119mm length spindle and a 68mm shell

  • 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

    All current Brompton bicycles use the 3/32 inch chain (made for Brompton by SRAM)

    The older 1/8 inch chain is (discontinued by Brompton from 2017) no longer available

    Newer Bromptons / sprockets all use the 3/32 inch chain width

    Previously these 3/32 inch chains were only used on derailleur (2 and 6 speed) Brompton bikes

    If you are in doubt which chain you need - choose this width and also get a new rear sprocket (ideally chain and sprocket should be changed at the same time). The 3/32 inch chains also have the benefit of using a SRAM powerlink - making installation of the chain easier.

    Older Bromptons with a single rear sprocket (1 / 3 / 5 speed) used to use 1/8 inch chains. These would only be used with an old sprocket - although newer 1 and 3 speed bikes also use the 3/32 inch chain

    We (and Brompton) recommend changing the rear sprocket(s) whenever the chain is changed (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)

    Chain size can be worked out based on the number of teeth on the front chainwheel and the number of teeth on the largest rear sprocket - as shown in the table below

    Chainring sizeLargest Rear SprocketChain requiredNote
    44T12T/13TQCHAIN096DRReduced gearing 3 speed / single speed
    44T15T/16TQCHAIN098DRReduced gearing 6 speed
    50T13TQCHAIN098DRStandard 3 speed Brompton
    50T16TQCHAIN100DRStandard 6 speed/Reduced gearing 2 speed
    54T13TQCHAIN100DRIncreased gearing 3 speed
    54T16TQCHAIN102DRStandard 2 speed/Increased gearing 6 speed
  • 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 42 items
Showing 1 - 12 of 42 items