Separate piece of CF on head tubes of CF frames.
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  1. #1
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    Separate piece of CF on head tubes of CF frames.

    You see it a lot on CF frames nowadays: there's a separate piece of carbon fiber - looks almost like a hatch - on the head tube, right under the stem.

    I've seen it many times but never figured out what it is. What is it?


  2. #2
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    That's the lowest headset 'spacer'. It matches the shape of the stem and the housing run through it.
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  3. #3
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    I'd call it a spacer. A bike company would call it a revolutionary innovation allowing for duel head tube length or some such nonsense.

  4. #4
    'brifter' is a lame word.
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    Quote Originally Posted by Jay Strongbow View Post
    I'd call it a spacer. A bike company would call it a revolutionary innovation allowing for duel head tube length or some such nonsense.
    No, they call it a spacer. You can't build the bike w/o it.
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  5. #5
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    My Gawd!!!! Did none of you watch "LOST"?????

  6. #6
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    Quote Originally Posted by cxwrench View Post
    No, they call it a spacer. You can't build the bike w/o it.
    Not every 'they' does.

    Parlee Altum X-wing - Fairwheel Bikes Blog

    "This simple top cap is interchangeable with two others of varying heights (8mm, 15mm, and 25mm – shown here with the 15mm). You can adjust your stack height +/- 17mm, making it one of the more adjustable frames on the market."

  7. #7
    'brifter' is a lame word.
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    Since that photo is of a Trek that's what I was talking about.
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  8. #8
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    Does Trek claim a function, reason or advantage?
    If the frame can't be built up without it I see it as a 'two piece head tube' not a 'spacer'.

  9. #9
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    Quote Originally Posted by Jay Strongbow View Post
    Does Trek claim a function, reason or advantage?
    If the frame can't be built up without it I see it as a 'two piece head tube' not a 'spacer'.
    It's the first spacer in the stack, it's required. All it really does is provide a way for the housing to get from the bar/stem into the frame. Given the shape of the frame this is the only way to do it.
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  10. #10
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    I could see that being a total PITA packing up for travel into a compact case.

  11. #11
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    Quote Originally Posted by Bremerradkurier View Post
    I could see that being a total PITA packing up for travel into a compact case.
    As far as I'm concerned the only way to travel w/ a bike is a SciCon or Evoc soft case. For a Madone I'd go for the SciCon...don't have to take the bars off.
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  12. #12
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    Technically a spacer/dust cap, technically not required. They build them into the frame for aero so people don't have to put another spacer above the height of the frame. Some part under the stem needs to rotate with the stem, can't just have the stem pushing down and rotating on the frame.

    Go check out some pro builds of the original Venge. They were slamming the stems so much, they'd put a shorter spacer in place of the factory provided aero spacer that integrated into the frame.

  13. #13
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    On the Trek you need to have that. You can't 'slam' the stem, the bottom of it would pinch the rear brake housing against the frame.
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  14. #14
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    On BMC Road Machine, definitely required as it's an integral part of the cable routing (I assume similar to the Trek). The bike/frame module comes with two versions. A high stack and a low stack. Choose your weapon.

    On Canyon, at least on my Endurace, it's not required, as it's just an additional spacer, although they provide one that is very thing.. something like 5mm. It provides a nice looking cover for the top of the headset.

    The biggest difference I can see between the Endurace and the other two bikes is that the cables (shift and brake) are routing through this piece on the Trek and BMC, whereas there are no cables to pinch on the Canyon, as the cables don't pass through the head tube internally.

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