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  1. #1
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    Brompton bottom bracket - light & compatible for light cranksets?

    Hey guys,

    I'm building a new bike from scratch and want to use the opportunity to swap parts.
    I read here and there, that people swapped their bottom brackets for lighter alternatives, but none is talking concrete models.
    So what fits the Brompton frame?

    Also, I'm eyeballing a lighter crankset, just not sure if there's an affordable version that's lighter than the bromptons...
    I heard, hollowtech is affordable, but how to determine, which bottom bracket fits brompton AND fits with light cranksets?

    Quite a complex topic I'm realizing...

    Anyone who can open my eyes

  2. #2
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    BB is determined by the crankset you are going to use so first pick your crankset. The BB will then be the width the crankset manufacturer recommends as will the type tapered, cottered, octilink etc. The threading will be determined by the frame you are using. Anyway first pick the crankset. Roger

  3. #3
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    I see.
    And there's no danger of ending up with a crankset that has no matching BB fitting a Brompton?

  4. #4
    Senior Member smallwheeler's Avatar
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    Quote Originally Posted by questionesse View Post
    Hey guys,

    I'm building a new bike from scratch and want to use the opportunity to swap parts.
    I read here and there, that people swapped their bottom brackets for lighter alternatives, but none is talking concrete models.
    So what fits the Brompton frame?

    Also, I'm eyeballing a lighter crankset, just not sure if there's an affordable version that's lighter than the bromptons...
    I heard, hollowtech is affordable, but how to determine, which bottom bracket fits brompton AND fits with light cranksets?

    Quite a complex topic I'm realizing...

    Anyone who can open my eyes


    there was a very informative thread about this a while back:

    The Brompton chainset upgrade/swap thread

  5. #5
    coprolite fietsbob's Avatar
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    Your BB shell Is standard BSC thread . Its close to the ground so 170 or shorter is Suggested.

    But when you are done you have to have the same Chainline as it is Now..

  6. #6
    PatronSaintOfDiscBrakes dynaryder's Avatar
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    Quote Originally Posted by questionesse View Post
    And there's no danger of ending up with a crankset that has no matching BB fitting a Brompton?
    Only if you go with BB or PF style cranks;they have external bearings which are held in cups in the frame.

    C'dale BBU('05 and '09)/Super Six/Hooligan8and 3,Kona Dew Deluxe,Novara Buzz/Safari,Surly Big Dummy,Marin Pt Reyes,Giant Defy 1,Schwinn DBX SuperSport,Dahon Speed Pro TT,Brompton S6L

  7. #7
    coprolite fietsbob's Avatar
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    And there's no danger of ending up with a crankset that has no matching BB fitting a Brompton?
    Cant say as a Sweeping Generality .. some may end up too far outboard to get the chain line right.

    it's in Pretty Close to where the rear fold axis outer plate of the rear portion, is ..

    seen folks putting carbon cranks on theirs [just Online none in Person]
    Last edited by fietsbob; 01-29-15 at 05:35 PM.

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    Seen that as well, but I'm not aware of any half-way affordable variant that wouldn't almost double the value of the bike when mounted.
    Or anyone knows a relative bargain for carbon cranks?

  9. #9
    coprolite fietsbob's Avatar
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    Live with whats on there if you cant afford the Bling you wish For.

    The old Arm attached to the chain ring crank was Probably lighter than the new 130 BCD spider crank ,

    but you replace the whole thing when the chainring is worn or you want a different size.



    Adding
    older square taper Dura Ace cranks are Nice , check eBay for reselling auctions . they are 130 BCD too
    Last edited by fietsbob; 04-21-15 at 04:28 PM.

  10. #10
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    I've noticed your tone before and I don't like it.
    In case you haven't noticed, you're not obliged to post - feel absolutely free to turn your attention to other threads and spare us your mood.
    And to at least make something constructive out of your posting - guess what - if I write I'm not aware of a cheaper priced crankset that means I did check around but didn't find any. Which brings us back to reaching out to other fellows who might have been in the same situation, I heard, that's what this forum is there for...

  11. #11
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    I believe what fietsbob was trying to tell you is carbon fiber and cheap can almost never be used in the same sentence. If carbon fiber is cheap I would be afraid there is something wrong with it and wouldn't use it. As you said it is bling factor but generally if you want bling you have to pay for it. Roger
    Last edited by rhenning; 01-31-15 at 05:24 PM.

  12. #12
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    Well, cheap is relative, I'm not expecting to get carbon for next to nothing.
    But for example with handlebars, saddles or seat posts are available in different price levels, which is why I can't agree with this oversimplification.

  13. #13
    PatronSaintOfDiscBrakes dynaryder's Avatar
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    Quote Originally Posted by questionesse View Post
    In case you haven't noticed, you're not obliged to post - feel absolutely free to turn your attention to other threads and spare us your mood.
    Actually,he does have to post in all threads. That's the only way he'll get his new post count back up to 40k.

    Quote Originally Posted by rhenning View Post
    I believe what fietsbob was trying to tell you is carbon fiber and cheap can almost never be used in the same sentence.
    Then that's what he should have said. With proper punctuation. fietsbob might have some constructive advise,but it's useless when you have to translate the code.

    Seriously fietsbob,would it kill you to type like a normal person? I know you can do it,you did it once to growl at me.

    C'dale BBU('05 and '09)/Super Six/Hooligan8and 3,Kona Dew Deluxe,Novara Buzz/Safari,Surly Big Dummy,Marin Pt Reyes,Giant Defy 1,Schwinn DBX SuperSport,Dahon Speed Pro TT,Brompton S6L

  14. #14
    Senior Member smallwheeler's Avatar
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    Quote Originally Posted by questionesse View Post
    Well, cheap is relative, I'm not expecting to get carbon for next to nothing.
    But for example with handlebars, saddles or seat posts are available in different price levels, which is why I can't agree with this oversimplification.
    what rhenning said is accurate.

    zipp carbon cranks with ISIS BB 108mm spindle (also note the use of a 33.9mm titanium seatpost):



    have you considered titanium?

    brompton titanium BB:


    swanky ti cranks:



    did you read this thread?


  15. #15
    Senior Member smallwheeler's Avatar
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    Quote Originally Posted by dynaryder View Post
    Actually,he does have to post in all threads. That's the only way he'll get his new post count back up to 40k.
    i made a note of when he reset his odometer. we're on track for celebrating 50k before the first official day of summer..


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    Just wanted to warm this up again as I haven't moved forward much.
    As I'm in the US and could bring back a crankset, I'm wondering if there's a specific SRAM carbon set that would fit the Brompton and I could take a look for.
    thx!

  17. #17
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    i would go for this combination: titanium seatpost (ebay), titanium handlebar (ebay), titanium bottom bracket (ebay), litepro crankset or KCNC crank arms (ebay) with KCNC chain ring (ebay), KCNC or litepro calipers (ebay), KCNC or litepro brake levers (ebay), titanium rail saddle, velocity rims, kojak tires, titanium nitride or titanium chains (ebay).
    Last edited by marxmini; 04-21-15 at 06:24 AM.

  18. #18
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    Or you can go full carbon: seatpost, handlebar, crank arms plus all the others i mentioned above.

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    Got a lot of carbon parts already - I'd just need some specific advise on which crankset would be affordable - I guess an SRAM would be an option in the US, but which fits?

  20. #20
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    sram s900 crank (triple, which should be around 117mm bb length), sram red (also in same length), fsa slk (many have used this crank, also in the same length). any of these should work for you.

    is your brompton a titanium lightweight?
    Last edited by marxmini; 04-21-15 at 06:42 AM.

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