Eccentric BB

Discussion in 'Cycling Equipment' started by Phil Holman, Jun 21, 2003.

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  1. Phil Holman

    Phil Holman Guest

    The chain on my newly acquired Canondale tandem is a tad on the slack side. There is a single bolt
    that goes through the eccentric part that is easily removed. Now what? I don't want to reef on it
    until I know how the mechanism works. Any help appreciated.

    Phil Holman
     
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  2. Mark Hickey

    Mark Hickey Guest

    "Phil Holman" <[email protected]> wrote:

    >The chain on my newly acquired Canondale tandem is a tad on the slack side. There is a single bolt
    >that goes through the eccentric part that is easily removed. Now what? I don't want to reef on it
    >until I know how the mechanism works. Any help appreciated.

    Just loosen the bolt a bit, insert a pin or hook spanner (depending on the design of your
    eccentric), and turn the eccentric until you get the desired chain tension. Don't make it TOO
    tight - I have had the best luck when I can get about 1/2" (1.2cm) of movement out of the chain
    at midspan.

    Mark Hickey Habanero Cycles http://www.habcycles.com Home of the $695 ti frame
     
  3. Phil Holman

    Phil Holman Guest

    "Mark Hickey" <[email protected]> wrote in message
    news:[email protected]...
    > "Phil Holman" <[email protected]> wrote:
    >
    > >The chain on my newly acquired Canondale tandem is a tad on the slack side. There is a single
    > >bolt that goes through the eccentric part
    that
    > >is easily removed. Now what? I don't want to reef on it until I know
    how
    > >the mechanism works. Any help appreciated.
    >
    > Just loosen the bolt a bit, insert a pin or hook spanner (depending on the design of your
    > eccentric)

    This is the part I'm not getting. How does a through bolt parallel to the BB axle keep the eccentric
    from turning?

    > and turn the eccentric until you get the desired chain tension. Don't make it TOO tight - I have
    > had the best luck when I can get about 1/2" (1.2cm) of movement out of the chain at midspan.

    I ride track so this part I'm familiar with. Phil Holman

    >
    > Mark Hickey Habanero Cycles http://www.habcycles.com Home of the $695 ti frame
     
  4. Phil Brown

    Phil Brown Guest

    >Just loosen the bolt a bit, insert a pin or hook spanner (depending on the design of your
    >eccentric), and turn the eccentric until you get the desired chain tension. Don't make it TOO
    >tight - I have had the best luck when I can get about 1/2" (1.2cm) of movement out of the chain
    >at midspan.

    In my experience not that simple. The Cannondale uses a wedge to tighten the eccentric and it often
    becomes stuck. Loosen the bolt a bit and tap it to loosen the wedge. If the bike's pretty new that
    may work. If it's older it may be stuck in which case more force may have to be used. Don't use the
    Allen, replace it with a hex head to beat on. Good luck. Phil brown
     
  5. Mark Hickey

    Mark Hickey Guest

    "Phil Holman" <[email protected]> wrote:

    >"Mark Hickey" <[email protected]> wrote in message
    >news:[email protected]...
    >> "Phil Holman" <[email protected]> wrote:
    >>
    >> >The chain on my newly acquired Canondale tandem is a tad on the slack side. There is a single
    >> >bolt that goes through the eccentric part
    >that
    >> >is easily removed. Now what? I don't want to reef on it until I know
    >how
    >> >the mechanism works. Any help appreciated.
    >>
    >> Just loosen the bolt a bit, insert a pin or hook spanner (depending on the design of your
    >> eccentric)
    >
    >This is the part I'm not getting. How does a through bolt parallel to the BB axle keep the
    >eccentric from turning?

    Sorry - you have a different eccentric than I do.

    >> and turn the eccentric until you get the desired chain tension. Don't make it TOO tight - I have
    >> had the best luck when I can get about 1/2" (1.2cm) of movement out of the chain at midspan.
    >
    >I ride track so this part I'm familiar with. Phil Holman

    Just remember the chain is a LOT longer than your track bike when you're checking the deflection.

    Mark Hickey Habanero Cycles http://www.habcycles.com Home of the $695 ti frame
     
  6. Phil Holman

    Phil Holman Guest

    "Phil Brown" <[email protected]> wrote in message
    news:[email protected]...
    > >Just loosen the bolt a bit, insert a pin or hook spanner (depending
    on
    > >the design of your eccentric), and turn the eccentric until you get the desired chain tension.
    > >Don't make it TOO tight - I have had the best luck when I can get about 1/2" (1.2cm) of movement
    > >out of the chain at midspan.
    >
    > In my experience not that simple. The Cannondale uses a wedge to
    tighten the
    > eccentric and it often becomes stuck. Loosen the bolt a bit and tap it
    to
    > loosen the wedge. If the bike's pretty new that may work. If it's
    older it may
    > be stuck in which case more force may have to be used. Don't use the
    Allen,
    > replace it with a hex head to beat on. Good luck.

    The tandem is a couple of years old but has less than 100miles on it. It has indications of grease
    oozing out of the joint so I'm thinking it will loosen up easily enough. Thanks for the info.

    Phil Holman
     
  7. Phil Holman

    Phil Holman Guest

    "Mark Hickey" <[email protected]> wrote in message
    news:[email protected]...
    > "Phil Holman" <[email protected]> wrote:
    >
    > >"Mark Hickey" <[email protected]> wrote in message
    > >news:[email protected]...
    > >> "Phil Holman" <[email protected]link.not> wrote:
    > >>
    > >> >The chain on my newly acquired Canondale tandem is a tad on the
    slack
    > >> >side. There is a single bolt that goes through the eccentric part
    > >that
    > >> >is easily removed. Now what? I don't want to reef on it until I
    know
    > >how
    > >> >the mechanism works. Any help appreciated.
    > >>
    > >> Just loosen the bolt a bit, insert a pin or hook spanner (depending
    on
    > >> the design of your eccentric)
    > >
    > >This is the part I'm not getting. How does a through bolt parallel to the BB axle keep the
    > >eccentric from turning?
    >
    > Sorry - you have a different eccentric than I do.
    >
    > >> and turn the eccentric until you get the desired chain tension. Don't make it TOO tight - I
    > >> have had the best luck when I can get about 1/2" (1.2cm) of movement out of the chain at
    > >> midspan.
    > >
    > >I ride track so this part I'm familiar with. Phil Holman
    >
    > Just remember the chain is a LOT longer than your track bike when you're checking the deflection.

    Good point and I'm looking at an inch of deflection at midspan. Like I said it's a tad too much.
    Phil Brown's post identifies the right kind of eccentric so I'm off to the hardware store to find a
    longer bolt. Thanks for your input.

    Phil Holman

    > Mark Hickey Habanero Cycles http://www.habcycles.com Home of the $695 ti frame
     
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