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Brompton gearing

Discussion in 'Tandem and Other Bikes' started by GAVSTER, 10 May 2008.

  1. GAVSTER

    GAVSTER Well-Known Member

    Location:
    Fife
    Guys,

    Is it possible to convert a Sturmey Archer Brompton three-speed into a six speed? There is a kit for SRAM hubs but nothing I've seen for Sturmeys.

    Also - any views on reducing the gearing on Brommies. The 50 tooth standard I've got is fine most of the time but sometime the hills are starting to get to my knees :-)

    Edinburgh cyclists will know some of the not massive but steep and cobbled streets :-)

    Cheers

    Gav
     
  2. Don't know about converting a SA hub but a call to Brompton will sort that, they're very helpful.

    I reckon Bromptons are over geared from the box but then I am a spinner, they sell smaller rings (with crank attached) and it may be possible to install a slightly bigger rear sprocket. For some reason the very smallest of the 'low gear option' rings is available only in steel. Yuk.

    We just received twenty Bromptons for our fleet. Including a Ti 2 spd. I happy bunny. ;)
     
  3. GAVSTER

    GAVSTER Well-Known Member

    Location:
    Fife
    Thanks for that Mickle - will call the Brommie boys.

    I think a smaller chainring might be the way forward before I need new knees.
     
  4. Yellow Fang

    Yellow Fang Guru

    Location:
    Reading
    I found the gearing on my L3 rather high. I was going to get a smaller chainwheel, but it wasn't compatible so the bikeshop put a bigger sprocket on the back. That's probably a better solution. I notice you could get 5-speed sturmey archer gear hubs for Bromptons for SJS cycles, although that would mean getting a new rear wheel built.
     
  5. stevew

    stevew Well-Known Member

    Location:
    Orpington
    Brompton do a 44T chainwheel and you can fit a larger rear cog 15 or 16 tooth is the biggest i think cos it will hit the rear frame if it's any bigger. A to B mag has lots of info on this
     
  6. Flying_Monkey

    Flying_Monkey Toll Collector on the Road to Nowhere

    The shop that did mine reckoned that the SRAM 3 converted to 6 was by far the best option other than the simple 2. The SA hub they didn't think much of at all.
     
  7. rogerzilla

    rogerzilla Über Member

    The answer to the original question is, I think, no. Brompton used to sell SA 3-speed and 5-speed (the SA 5-speed is a bit of a duffer), then when SA went bust, before the SunRace rescue, they switched to SRAM and found they could get two sprockets on a modified SRAM 3-speed.

    Now all the 3-speeds are SA and all the 6-speeds are SRAM.
     
  8. jonesy

    jonesy Legendary Member

    I've got a T5 with the SA 5 speed (the variety with the blue band on the indicator rod; probably pre-SunRace though). It ran completely trouble free for the first 6 months or so (using most working days at about 10 miles per day); then started slipping out of adjustment and, no matter how carefully I tweak the adjustment, it always jumps occasionally on at least one gear. Anyone got any tips? Is it practicable/ cost effective to get it replaced with a three speed?
     
  9. rogerzilla

    rogerzilla Über Member

    It should be possible, but Brompton modified the rear dropouts slightly when they started using SRAM hubs, and your bike will pre-date that.

    I'm not sure of the rear spacing, but people have apparently bodged Rohloffs in there.
     

  10. Brompton still use Sram and SA hubs. You can get a Rohloffs in as im told by the head of the head of tech At Brompton But you can Fu.K the frame.
     
  11. rogerzilla

    rogerzilla Über Member

    One solution is to go off and ride fixed for a bit.

    3 gears will then seem rather decadent.