Tips for designing a dropper friendly frame- Mtbr.com
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  1. #1
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    Tips for designing a dropper friendly frame

    When reading through dropper failures, of whatever brand, scant are the reasons why.

    Was it a design failure of the post itself, or were there other frame design contributing factors?

    It seems to me:

    1. Seat tube angle...slacker creating more friction stress when loaded.

    2. Internally butted seat tube...creating a catch point should there be a failure of pressure containment... and a resulting expansion or bursting of the post?

    Do any builders have any thoughts on how tubing choice and design MAY play a role? I recognize that things are what they are, but if one understands the pros and cons of a given frame design...it could factor in with dropper choice?

    Any thoughts would be welcome from builders or dropper users with suggestions, concerns.
    "Courage is being scared to death and saddling up anyway" John Wayne

  2. #2
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    Dropper post failure has a lot more to do with poor droppers than it does goofy frame design. The only thing frame builders can do is run a large seat tube (which influences how the frame handles). Seat angle shouldn't matter and internal/external butting doesn't matter.

    I do double integrated clamps on my mtb frames. They're not really necessary cuz i run the reliable dropper, but why not? Double clamp seat collars are available aftermarket.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  3. #3
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    Providing for internal routing will ensure compatibility with some of the more reliable posts available (many new models don't have external options, aka X-Fusion Manic or Bike Yoke Revive).

    Avoiding 27.2 diameters will provide for far, far more dropper options and, generally speaking, better reliability.

    Most dropper failures involve the hydraulics, damping and sealed cartridges that act as the spring. Severely slack seat angles (like on some old interrupted seat tube designs) could conceivably add to side loads that stress some of the components (keys and keyways) but that situation seems unlikely in a handbuilt frame. I am skeptical that there are meaningful differences for the dropper among the common range of seattube angles, even in offset or curved tube designs where actual angle is > than effective angle.

    If your design objective can tolerate a 34.9 seattube i.d., the Bike Yoke Revive MAX 34.9 is arguably the strongest, most reliable dropper available. imho, fwiw

    Ultimately there are huge dropper reliabiity gains possible "thru framebuiding" but it will involve integration: using the seattube as the effective outer tube of the dropper, as in the Eightpins design.

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