Trying to understand CBF- Mtbr.com
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  1. #1
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    Trying to understand CBF

    Can someone explain how the CBF concept is (or acts differently than a single pivot), given the IC stays right in the same spot as a single pivot would? Just trying to understand the technical details. I owned a Riot and thought it rode great.

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    Magic+science =CBF


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    Just wondering, did you read their explanation on their website? Otherwise, owning a Balance just makes me simply agree with you.

  4. #4
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    Quote Originally Posted by jaks View Post
    Can someone explain how the CBF concept is (or acts differently than a single pivot), given the IC stays right in the same spot as a single pivot would? Just trying to understand the technical details. I owned a Riot and thought it rode great.
    Jaks,
    The IC of a CBF isn't in one spot. It is in front of the chainring and moving. The "CC" or Center of Curvature is what you are thinking about. And yes- it can be isolated to be in one spot- like it is on a riot or balance. But the Layout of the Revel bikes has the CC moving across the top of the chainring.

    I know it is complicated to understand. But I'll do my best to explain.

  5. #5
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    I guess the confusing part is the IC vs the CC. If you put a singe pivot right where the CC is on a Riot, would the bikes act differently, and why?

  6. #6
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    Quote Originally Posted by jaks View Post
    I guess the confusing part is the IC vs the CC. If you put a singe pivot right where the CC is on a Riot, would the bikes act differently, and why?
    Yes.
    If a single pivot rode as good as a CBF or any multi-link bike- the industry would have never built anything but single pivots. The magic is how a multi-link suspension can isolate the brake and pedal forces.

  7. #7
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    Quote Originally Posted by cSquared View Post
    Yes.
    If a single pivot rode as good as a CBF or any multi-link bike- the industry would have never built anything but single pivots. The magic is how a multi-link suspension can isolate the brake and pedal forces.
    Single pivot with a floater and idler at the pivot get it done also.
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  8. #8
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    Floater and idler would add weight and drag so weight weenies frown on that, unless it's on a down hill bike. I don't think majority of consumers would would want it either.

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    Quote Originally Posted by ScottieM8 View Post
    Floater and idler would add weight and drag so weight weenies frown on that, unless it's on a down hill bike. I don't think majority of consumers would would want it either.
    Pretty sure weight weenies stopped being the main focus of frame makers many moons ago. Added drag from an idler is minimal, and floater adds none. It's actually a good, simple solution, but you're right; majority of buyers these days would likely rather have something complicated, expensive, and hard to keep going long-term. Cuz 'progress'.
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  10. #10
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    Quote Originally Posted by slapheadmofo View Post
    Single pivot with a floater and idler at the pivot get it done also.
    yes- but only the I-track versions of the idler. Like the new Commencal and Norco or the old Balfa bb7, if they added the floater....

  11. #11
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    Quote Originally Posted by cSquared View Post
    yes- but only the I-track versions of the idler. Like the new Commencal and Norco or the old Balfa bb7, if they added the floater....
    Looking at pics of those - so the idler position changes as the suspension cycles?
    What does that gain versus a static idler position concentric to the pivot point of a single pivot, add some pedal feedback back in?
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  12. #12
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    Quote Originally Posted by slapheadmofo View Post
    Looking at pics of those - so the idler position changes as the suspension cycles?
    What does that gain versus a static idler position concentric to the pivot point of a single pivot, add some pedal feedback back in?
    An idler on the pivot will pedal like a BB concentric pivot. Very inefficient. The CHAINLINE is the key. If not directed at the IC or single pivot point it will pull into the travel with every pedal stroke. (It's a tug-of-war game, above the pivot = pulling into travel. below the pivot = pulling down.)

    The idler on the swingarm (like the I-track setup) can give you a great balance. No pedal-kick/chain-stretch and the chain will pull down under pedal force, on the swingarm and give efficient pedaling.

  13. #13
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    Quote Originally Posted by cSquared View Post
    An idler on the pivot will pedal like a BB concentric pivot. Very inefficient. The CHAINLINE is the key. If not directed at the IC or single pivot point it will pull into the travel with every pedal stroke. (It's a tug-of-war game, above the pivot = pulling into travel. below the pivot = pulling down.)
    Interesting, thanks.

    So maybe a jackshaft rather than an idler would be better as far as isolating the suspension from pedaling forces (though it sounds like totally eliminating them is not really the ultimate goal for most designs, rather being able to dial them in)?
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  14. #14
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    Quote Originally Posted by slapheadmofo View Post
    Interesting, thanks.

    So maybe a jackshaft rather than an idler would be better as far as isolating the suspension from pedaling forces (though it sounds like totally eliminating them is not really the ultimate goal for most designs, rather being able to dial them in)?
    Jackshaft does TOTALLY isolate the chain-stretch/pedal-kick from the system. Although they have the same Anti-squat as the BB concentric pivot.

    The idler is light and simple to do.

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    Quote Originally Posted by cSquared View Post
    Jackshaft does TOTALLY isolate the chain-stretch/pedal-kick from the system. Although they have the same Anti-squat as the BB concentric pivot.

    The idler is light and simple to do.
    Thanks for confirming. Been trying to make some decisions on a (hopefully near-)future build. Thinking an idler is probably good enough for me, though I kinda like the idea of being able to run SS on an FS.
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