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  1. #1
    mtbr member
    Reputation: itsdoable's Avatar
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    Jan 2004
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    1,878

    Rohloff, Haro, retro-fitted eBB

    This is cross posted from the SS forum, where the posts for this eBB started out. (Review: Forward Components eBB for conventional BB shells)

    Forward Components made an eBB that is retrofittable into most 68mm BB shells, which allows ~15mm of motion. I've been eyeing the similar Tr!ckstuff Exzentriker eBB for my FS Rohloff project, but had been bulking at the price - and in retrospec, I'm not sure the Exzentriker would clear the link on this frame.

    I've had a Rohloff hub on my Haro Sonix without a tensioner using a magic ratio, but I'm stuck with a higher gear range than I like, and no way of adjusting for chain wear (except replacing the chain). The Sonix is one of the few suspension frames that have a fixed BB to dropout distance, allowing tensionerless setups with SS and IGHs. It also has a 73mm BB shell, which is recessed inside the concentric links:



    The ID of the link is just shy of the Forward Components eBB cup, so to make the cup clear, I had to remove about 0.5mm from the base of the non-drive side cup.



    The Drive side is not recessed, so that cup fits as is.

    After installation, the cup looks like it actually belongs there:


    Again, I'm using a FC-M532, which has an interface that can clear the larger cups without extra spacers, allowing this to be installed on a 73mm BB shell (FC only specs this eBB for a 68mm BB shell). The chain stays on this frame have lots of clearance around the cups to access the set screws, even if the setscrew lines up with the cs.

    Original Post from Forward Components announcing the eBB:
    Another eccentric bottom bracket for standard frames.

    Original post for Haro Sonix with Rohloff:
    Sonix and Rohloff







    On another note, I recommend that you check the credentials of the mechanics tuning your suspension.

    "...you have too much rebound..."

  2. #2
    trailbuilder
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    Join Date
    May 2007
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    4

    eBB okay for Haro, not for Cove G-Spot

    Thanks for the nice close-up pix.

    It's nice to see there is at least one relatively clean solution for a full-suspension Rohloff/SS without a chain tensioner (or magic ratio). Will we ever see a production bike that meets this design goal?

    Now I can see why the retrofit eBB will work very well with the Haro, since the bottom bracket shell is locked into the rear triangle, and the rear triangle rotates as a unit.

    Earlier I had thought an eBB insert (like the Forward Components or the Trickstuff Exzentriker) would work with the Cove G-Spot in a similar way.

    However, the geometry of the G-Spot is a little different: the chain stays rotate around the outer shell of the bottom bracket, which is fixed to the front triangle. With an eBB insert, the center of the chainring would not be concentric with the rotation of the chain stay, so there would be some variation of the chain length as the rear suspension moves.

    On the G-Spot, the eBB insert is fixed with respect to the front triangle, not with respect to the chain stay. So it looks like there is no benefit to using an eBB insert on the G-Spot - it cannot be used to make the adjustments needed for a good Rohloff/SS installation.

    - Paul

  3. #3
    Rohloff
    Reputation: bsdc's Avatar
    Join Date
    Apr 2006
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    1,517
    That's a nice Rohloff setup. I'd love to get a Sonix 29er but they decided to go 650b. Ugh!

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