I want to run a brake hose through my steerer tube and need space for a clean exit.

My idea is to attach a kevlar spoke to the crown of the fork using the fender attachment point. Then I can run that inside the steerer to a length of threaded tube which the steerer cap is screwed into. I will fit a sleeve at the top of the fork to handle the pressure from the stem.

The Kevlar is easily strong enough for the preload and then my steerer is empty and I don't need to make a custom expander plug.

Aside from the hassle of it, do any of you experts see a problem with this?

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    Or you could use a bmx style cap and bolt designed for purpose like the one dia-compe make etc
    – Noise
    Sep 17, 2021 at 18:16
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    Nice idea! At least for carbon steerer tubes I’ve heard that the expander plug is actually necessary to avoid deformation of the tube from the clamping forces of the stem. So you can’t just take it out. Not sure how true it is though.
    – Michael
    Sep 17, 2021 at 19:21
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    At least for carbon steerer tubes I’ve heard that the expander plug is actually necessary to avoid deformation of the tube from the clamping forces of the stem It better not be. No manufacturer requires a steerer tube to be cut short enough that the stem must clamp on where the expander plug is. For example, such instructions are completely lacking in the Trek Emonda assembly manual: trek.scene7.com/is/content/TrekBicycleProducts/… Sep 17, 2021 at 23:15
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    So you're doing a Potts mod ? i128.photobucket.com/albums/p191/mcseforsale/DYNO_RESTORATION/…
    – Criggie
    Sep 17, 2021 at 23:48

2 Answers 2


Thanks but I found a better solution. A plug with ample space for routing. I will fabricate a custom top cap to go with that.



  • Excellent find. Seems like a much better solution.
    – Adam Rice
    Oct 4, 2021 at 0:27
  • Really nice piece of engineering too. I am surprised this design isn't more popular. Clever German guy with great service. Unfortunately shipping cost more than the piece itself! Oct 4, 2021 at 1:02
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    Ah, intend. The guy is a technical genius with pricing to match.
    – MaplePanda
    Oct 4, 2021 at 23:28

The top cap serves two purposes:

  1. To set bearing preload in the headset. This is convenient but not at all essential; you can set preload using any reasonable method of putting downward pressure on the stem while you clamp it.

  2. To prevent injury in a crash.

You need the top cap for (2) but not for (1) which means your kevlar spoke idea is unnecessary. I suppose you're going to drill a couple holes (or a slot) in it for your brake hose and dynamo wire. Then I suggest you simply glue the top cap to the stem, it only needs to hold the force of the hose and wire and if it pops off it isn't going to cause a crash, so you don't even need "permanent" adhesive, you can use glue which is just moderately strong so the top cap can be separated from the stem later if needed.

As usual, you need your steerer tube cut just a bit (~3mm) shorter than the top of the stem clamp, so the top cap can sit in place without hitting the steerer tube. I assume you have no spacers above your stem.

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