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I have an Origin8 compression plug 90mm long with recommended torque of 8Nm. But it can't be inserted fully into the Hylix carbon fork I bought online as there's lots of epoxy blocking the tube in the last 10mm of space the plug requires to be fully inserted (given the length to which the steerer has been cut, ~7 inches, 17.5cm). The obstruction extends up to about 9cm above the fork crown. Rather than try to drill some of that stuff out, I bought a slightly shorter plug that is only 81mm in length.

The recommended torque for the 81mm plug is 10Nm (per the manufacturer's website). I can't find any technical info on Hylix, so I'm wondering if 10Nm is OK, as it is a good deal higher than recommended torque on the Origin8.

The Whisky compression plug instructions say to tighten their plug to only 1.6Nm, so clearly there must be quite a difference in the design of these plugs, or quite a wide range of opinion on the proper torque, or that number is a typo.

Is there any way the consumer can make fact-based judgments on such things? Is the thickness of the steerer tube wall the determining factor? It is 2.65mm

“People often make the mistake of thinking that the plug is solely to preload the headset bearings,” he [Raoul Luescher of Luescher Teknik in Melbourne, Australia] said. “However, due to most carbon steerers not having much in the way of hoop strength, due to the difficulty in laying down 90-degree fibers in a production environment with the process used, the plug is important to contain the hoop loads from the stem clamp. Thus I do not recommend ultralight or poorly designed or installed plugs in most steerer tubes as we see lots of cases of delamination caused by the stem clamp.”

https://cyclingtips.com/2017/05/cane-creek-eenut-review/

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  • compression plug 90mm long Get a shorter compression plug. Feb 7, 2021 at 22:04
  • @AndrewHenle Read before offering advice. I did get a shorter plug.
    – Tim
    Feb 8, 2021 at 11:14
  • All the compression plug does is hold the top cap in place while you tighten the clamp bolts on the stem. It's literally useless after that. Feb 8, 2021 at 11:18
  • @Andrew Henle: Why do compression plugs come in different lengths?
    – Tim
    Feb 8, 2021 at 11:37
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    LOL. I sure hope you don't have a carbon fiber seatpost. You know, a hollow carbon fiber tube clamped onto by something and without some piece of metal inside, which you apparently think is necessary for a carbon fiber tube that gets clamped to function safely. Because that carbon fiber seatpost - without that internal metal reinforcement - is supporting a whole lot more weight than the steerer tube, and it's just sitting there waiting to break off and stab you right in the nether regions. Why, it's gonna snap right off just like all those steerer tubes without that huge plug! Feb 9, 2021 at 12:26

1 Answer 1

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Some things to consider:

  • The plugs only purpose is to be strong enough to not move up when you tighten the headset down.
  • The steerer will be clamped by the stem, so the stem will reinforce the steerer once clamped.
  • The top cap recommended torque is probably 4-6Nm.
  • Support the top of the steerer from crushing. Although it is often recomended to add a 5mm spacer ontop of the stem so the top of the stem in not flush with the top of the steerer to help with this.

So my advice if you're worried about the steerer's integrity would be tighten the plug to a lower spec than you think and try it with the top cap, only tighten the plug further if the top cap pulls it up.

As the stem will clamp the steerer with more force than the plug expands with, you shouldn't worry about the plug damaging your steerer as you ride.

So, torque specs are in general only advisory in the sense that they will a min and max value. If you're careful and mindful of what you're doing, you don't need to look at the plug torque at all, just tighen enough so it doesn't ride up, making sure at no point you pass a damaging amount of torque (more than 10-13Nm in this case).

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    I suspect the plug is also to support the steerer tube from the inside, and the generous length means that support goes down below the top bearing.
    – Criggie
    Feb 8, 2021 at 11:00
  • Only at the top, I will edit to add this, you will destroy the threads on the stem way before you start crushing the steerer further down from the top.
    – abdnChap
    Feb 8, 2021 at 11:15
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    @Criggie It might very well do that, but as I've yet to see a single failed steerer tubes on all those bikes that use short compression plugs, I'd say it's a useless feature. Feb 8, 2021 at 11:19
  • I would say a 90/80mm plug is way overkill. Don't need anything bigger than 40ish-mm really.
    – abdnChap
    Feb 8, 2021 at 11:21
  • @abdnChap My underlying question is, in the absence of guidance from the manufacturer (who might be unknown) how does the DIYer come by the knowledge that torque in excess of 13Nm can damage a particular carbon steerer?
    – Tim
    Feb 8, 2021 at 11:29

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