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  1. #1
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    How far below the stem should the bottom of an expander plug sit?

    Title says pretty much everything. I've found a long expander plug (Specialized) to install on my steerer tube. Considering where my steerer will sit, the expander will extend about 4mm under the lower part of the stem.


    From a structural standpoint, would an even longer plug be an even better idea, putting two stress points further apart. Or is this setup more than enough?

    On a related note, could it be a good idea to use blue loctite on both the expander bolt and top cap, to reduce possible slippage? Or is it pointless since the stem holds everything in place once tightened?

    And finally, spesh expander has a recommended torque of 9Nm. That seems unusually high... Is it? The stem is recommended at 4.5Nm

    Thanks all!

  2. #2
    'brifter' is a lame word.
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    In this case more is usually better. Is it necessary? The manufacturers say no by way of their specs (for example: 90mm from top of headset cover to top of stem), but it can't hurt...and can only help, by offering a longer area of supported steerer.
    I would not use Loctite...only grease. Don't worry about the torque spec, it's been engineered and tested, it won't be a problem. Some of them are 10Nm.
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  3. #3
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    Quote Originally Posted by cxwrench View Post
    In this case more is usually better. Is it necessary? The manufacturers say no by way of their specs (for example: 90mm from top of headset cover to top of stem), but it can't hurt...and can only help, by offering a longer area of supported steerer.
    I would not use Loctite...only grease. Don't worry about the torque spec, it's been engineered and tested, it won't be a problem. Some of them are 10Nm.
    Thanks, once again very helpful.

    The more I search, the more I think my first question is purely theoric, as I can't find anywhere on the web a plug longer than the specialized one.

  4. #4
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    I don't know the answer for sure, but I can make an educated guess based on what I know about the tasks this device performs.

    1. It serves as a way to grip the fork and tighten the steerer assembly (i.e. like a star nut).

    2. It reinforces the segment of steerer tube that is covered by the stem.

    3. Reinforces the steerer tube below the stem, if there is any of this device that extends below the stem.

    Based on these tasks, items 1 and 2 require only that the expander extend the length of the stem, and no more. Item 3, however, requires extension of the device below the stem in order to resist the bending forces the steerer will encounter. The longer the expander extends, the better.

  5. #5
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    Quote Originally Posted by cxwrench View Post
    In this case more is usually better. Is it necessary? The manufacturers say no by way of their specs (for example: 90mm from top of headset cover to top of stem), but it can't hurt...and can only help, by offering a longer area of supported steerer.
    I would not use Loctite...only grease. Don't worry about the torque spec, it's been engineered and tested, it won't be a problem. Some of them are 10Nm.
    Probably my last question on the subject... I finally found some free time and went ahead with the installation of the Specialized expander plug. Torqued it under spec (7Nm instead of the specified 9Nm, as it felt already pretty tight and super secure). Just to make sure, I inspected the steerer after the installation of the expander and the 'metal ruler test' showed me a very slight bulge at the bottom part of the expander (which wasn't there with an empty steerer). I can also notice the slight bulge if I pay close attention while moving a spacer up and down, but I can't feel it by running a finger up and down.

    How normal is this? I'm inclined to think it's OK and I think my steerer is subject to this kind of deformation regardless of what expander is used, as the stock expander used to leave me with a bottom stem bolt that would not clamp as far as the upper one. A few other Synapse owners have reported the same.

    I'm becoming a bit OCD with this, but I just want to take every precautions to make sure I won't be eating gravel this summer.

  6. #6
    'brifter' is a lame word.
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    The expander will definitely cause the steerer to expand...you can notice this when pulling a stem then spacers off a fork w/ an expander tightly installed. Sometimes you can't get the spacers off if they're snug. You loosen the expander a bit and the spacers come right off. It's totally normal.
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  7. #7
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    Thanks, I'll sleep better!

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  8. #8
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    I prefer a glued-in place plug. No expansion problem, but you have to get everything set-up before gluing in place.

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