EBB possibilities question??- Mtbr.com
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  1. #1
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    EBB possibilities question??

    The new XT/ XTR bottom bracket has the bearings on the outside of the shell, right? Would it now be possible to build an EBB which would fit inside a standard shell and use the new Shimano BB with the bearings outside the shell? This would allow for retrofit of an EBB onto ANY bike. Or am I missing something?

  2. #2
    hispanic mechanic
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    Quote Originally Posted by nmcculloch
    The new XT/ XTR bottom bracket has the bearings on the outside of the shell, right? Would it now be possible to build an EBB which would fit inside a standard shell and use the new Shim ano BB with the bearings outside the shell? This would allow for retrofit of an EBB onto ANY bike. Or am I missing something?
    The bb threads of the new external bb system is still the same size as the old standard bb, which is why they work in standard frames. The external bearing set-up just gives you the ability to use larger bearings, for greater service life and a larger bb spindle. So no, you still need a regular ebb in order to get chain tension.
    Hope that helps,

    the los
    Whiskey is my yoga.

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  3. #3
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    I just built me up a new bike with Bushnell EBB and external bearing XT M-760 cranks. Works like a champ - no worries.

  4. #4
    hispanic mechanic
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    I think what he's asking...

    Quote Originally Posted by ssmike
    I just built me up a new bike with Bushnell EBB and external bearing XT M-760 cranks. Works like a champ - no worries.
    Is whether you can fit some sort of smaller ebb into a standard bb shell, not if the M-760 system will work in a normal ebb.
    Or am I reading his question incorrectly?

    the los
    Whiskey is my yoga.

    dongerparty.com

  5. #5
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    Quote Originally Posted by sslos
    Is whether you can fit some sort of smaller ebb into a standard bb shell, not if the M-760 system will work in a normal ebb.
    Or am I reading his question incorrectly?

    the los

    Yep, you're right. I'm loopy. The answer to his original question is still nope as you stated.

  6. #6
    hispanic mechanic
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    Hey Mike...

    Quote Originally Posted by ssmike
    Yep, you're right. I'm loopy. The answer to his original question is still nope as you stated.
    Not to totally hijack this thread, but I was wondering how much you've used the ebb on your 'cross bike to play around with effective bb height. Hey! I guess it's not a complete hijack, since it still deals with an ebb question, right?

    the los
    Whiskey is my yoga.

    dongerparty.com

  7. #7
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    Quote Originally Posted by sslos
    Not to totally hijack this thread, but I was wondering how much you've used the ebb on your 'cross bike to play around with effective bb height. Hey! I guess it's not a complete hijack, since it still deals with an ebb question, right?

    the los
    Aye, laddie. I don't have an EBB on my pure 'cross bike - standard geared fare. On my 26" single, I did set it up as high as possible just to get a bit higher bb height (not sure of the exact measurement). I did just finish an "experiment" with a mistake of a 26" ss frame where I put a 700c x 44 moto raptor in the rear, 29" 2.1 nano in front (with a KM fork), W T B drops with old school W T B / Suntour thumbshifter that allows me to run it as a 2-speed - kind of nice, a gear to ride to the trails and then a trail gear. The mistake was a derailleur hanger on the ss frame. So, with the big wheels on the 26" frame and the ebb at the bottom, I'm at a 13" bb height. Not bad.

  8. #8
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    Quote Originally Posted by ssmike
    I just built me up a new bike with Bushnell EBB and external bearing XT M-760 cranks. Works like a champ - no worries.
    Ok to continue ssmikes hijack, do any and all ebb's work with outboard bearing bb's or do some of them have nuts/etc that would be blocked by the bearing shells?

  9. #9
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    Quote Originally Posted by icegeek
    Ok to continue ssmikes hijack, do any and all ebb's work with outboard bearing bb's or do some of them have nuts/etc that would be blocked by the bearing shells?
    I don't see any reason why all external bb's should not work with any ebb types. I'm using a Bushnell expanding wedge type and the external bearings do not interfere with the ability to tighten or adjust the ebb. The grub screw type or the split clamp type would also have no issues. All outboard bearings (S himano, R aceFace, Truv ativ, F S A) will have total compatibility with ebb's.

  10. #10
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    You all say no but I think yes.

    It is true that the Shells that hold the larger BB Bearings have the same size thead but these need not be used. If someone was to machine up a smaller Eccentric to fit into a standard shell and that eccentic would have external carriers for the bearings.

    It wound have nowhere near as much adjustment as say the Phil W, Bushnell or the Cannondale but you must then ask the question. Why do we need as much adjustment as they give.

    An SS bike only requires 1" of chain length adjustment to allow and chainring/sprocket combination.

    The reason all EBBs give more than this stems from there original intended use, which is to take up slack between the chainsets of the stoker and the steerer on a Tandem.

    Please tell me if I am talking rubbish.

    P::..

  11. #11
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    Quote Originally Posted by nightfire
    It is true that the Shells that hold the larger BB Bearings have the same size thead but these need not be used. If someone was to machine up a smaller Eccentric to fit into a standard shell and that eccentic would have external carriers for the bearings.

    It wound have nowhere near as much adjustment as say the Phil W, Bushnell or the Cannondale but you must then ask the question. Why do we need as much adjustment as they give.

    An SS bike only requires 1" of chain length adjustment to allow and chainring/sprocket combination.

    The reason all EBBs give more than this stems from there original intended use, which is to take up slack between the chainsets of the stoker and the steerer on a Tandem.

    Please tell me if I am talking rubbish.

    P::..
    I think it could be done, but only with a square taper type of axle (17mm diameter). The larger pipe spindles are too large in diameter to fit the following criteria: fit through a bearing, have enough room inside a standard bb shell to rotate through an eccentrec motion and not touch the inside of the bb shell.

    It might be possible to build up an ENO-like bottom bracket with a 17mm square taper axle that would have just enough movement to tension up a chain.

    The problem will be the threads and fixing the mini-eccentric into the shell. The external carrier for the bearings would have to press or thread into the eccentric. How would the eccentric be held into the shell? It can't be threaded into it.

    I'd say an ss bike needs much less than 1" of chain adjustment.

    Not a hopeless cause, but one that would require a lot of thought and some dough to make samples.

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