Which carbon steerer plug

Fabius
Fabius Posts: 56
edited November 2014 in Workshop
Hi,

I've just taken delivery of a new frame and carbon fork for a new build. Happy with everything I need to do with the steerer in terms of measuring, cutting etc but I have one niggle - they've sent me two carbon steerer plugs.

I've only ever used star nuts in non-carbon steerers - can someone look at the picture and tell me (from experience ideally) which of the two is going to do a better job, or does it really not matter?

Thanks

Comments

  • maddog 2
    maddog 2 Posts: 8,114
    the right one.
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • Fabius
    Fabius Posts: 56
    Cheers, I have to say it looks and feels like a better part.
  • Ouija
    Ouija Posts: 1,386
    Just remember you need to expand the bung long before you put the top cap anywhere near it as a lot of people make the mistake of thinking screwing in the top cap expands the bung (it does, but only after it's dragged it to the top of the steerer). This is typically done with a larger sized allen key than the one you use on the top cap.
  • Fabius
    Fabius Posts: 56
    Yeah nice one Ouija, I had clocked that but it will still need a bit of fine adjustment to get the top cap nice and snug with the right pre load.
  • ugo.santalucia
    ugo.santalucia Posts: 28,312
    Good luck... my view on expander bungs is that they are all shxt...
    left the forum March 2023
  • Fabius
    Fabius Posts: 56
    Hey Ugo,

    Surely all it really needs to do is provide enough friction inside the steerer to get the preload set and then once the stem bolts are tightened they take the lion's share of that job?

    To be honest, I don't like the idea of an expanding plug inside a carbon tube but it seems like a good enough solution for careful people?

    What's the alternative?
  • earth
    earth Posts: 934
    I've had examples of both. The left one looks like a good idea because the plug looks like it would double as reinforcement for the steerer tube clamping zone.

    In practice it does not work. I suspect it is because it does not evenly apply pressure to the inside of the steerer tube, probably only at the bottom, therefore it slips.
  • ugo.santalucia
    ugo.santalucia Posts: 28,312
    Fabius wrote:
    Hey Ugo,

    Surely all it really needs to do is provide enough friction inside the steerer to get the preload set and then once the stem bolts are tightened they take the lion's share of that job?

    To be honest, I don't like the idea of an expanding plug inside a carbon tube but it seems like a good enough solution for careful people?

    What's the alternative?

    In my experience they don't do the job of providing enough grip. I had to wrap it in folded sandpaper to get enough grip. The concept is flawed and they are a hit and miss. I honestly can't believe that 21st century engineering can't do better than this crap. I think it's manufacturers' laziness
    left the forum March 2023
  • Fabius
    Fabius Posts: 56
    earth wrote:
    The left one looks like a good idea because the plug looks like it would double as reinforcement for the steerer tube clamping zone.

    In practice it does not work. I suspect it is because it does not evenly apply pressure to the inside of the steerer tube, probably only at the bottom, therefore it slips.

    Exactly what I thought and the main reason that I asked the question, thanks.
    ugo.santalucia wrote:
    In my experience they don't do the job of providing enough grip. I had to wrap it in folded sandpaper to get enough grip. The concept is flawed and they are a hit and miss. I honestly can't believe that 21st century engineering can't do better than this crap. I think it's manufacturers' laziness

    The one on the left is longer, but it is glass smooth and as Earth says I thought that it would give additional support where the stem bolts are torqued up. The one on the right by comparison has a beautiful surface, like 120 grade sandpaper. It will grip properly inside the steerer. I wonder how much the benefit of the left's length is perceived, especially if pressure is not evenly applied, whereas the right's will definitely provide better grip.

    I'm putting it all together tomorrow so I'll let you know how I get on. Ugo, I agree, it's a similar issue to frame protection - we shouldn't have to protect frames on bikes from cable rub, they should be built in a way that avoids it.
  • earth
    earth Posts: 934
    The long one that I tried had a sandpaper finish and it still didn't work. The process of expanding the bung before putting the stem on is key. Note that you might want to expand it as much as you can but then you may find the stem won't fit on the steerer tube because it has bulged.

    I agree with Ugo that they are very hit and miss. I found after fitting one that it loosened over a period of 2 weeks and I kept having to fettle with it. Eventually I mastered the expanding the bung process but sadly I've forgotten the knack now. Sometimes I wonder if a smear of epoxy resin around the bung might be the answer. Seems a bit too permanent but once fitted you never really want to remove them. Plus a star nut cannot be removed once fitted.
  • keezx
    keezx Posts: 1,322
    earth wrote:
    T Plus a star nut cannot be removed once fitted.

    Give me your steerer and I'll remove the starnut in 30 seconds.
  • mikenetic
    mikenetic Posts: 486
    I've used the ones that Columbus supply with their forks a few times, and I have to say I've not had any issues. They have a diamond pattern surface that seems to grip pretty well.

    Wonder if carbon assembly paste might help in the event that the bung slips?
  • earth
    earth Posts: 934
    Keezx wrote:
    earth wrote:
    T Plus a star nut cannot be removed once fitted.

    Give me your steerer and I'll remove the starnut in 30 seconds.


    I guess they can be removed then :)


    What if some manufacturer made a steerer tube that had like a bulk head bonded into it with a thread in the centre? Effectively a bonded in bung. If they made it deep enough inside the steerer there would still be enough tube above it to allow for it to be cut to size. All you would need is a longer bolt. If the bung was carbon fibre then the absence of a metal bung would compensate for the extra weight of a longer bolt.

    Done.
  • keezx
    keezx Posts: 1,322
    Not a bad idea, i have considered to make a similar solution for the one and only carbon steerer I ever had.
    Problem was that the steel bolt was still way too heavy and a long alloy or titanium bolt too expensive or not available.
    I ended up glueing a piece of wood in the steerer with a nut.
  • rrsodl
    rrsodl Posts: 486
    edited November 2014
    I use one that came with my Van Nicholas fork, it looks a bit like the one on the left. Tightened to, if I remember correctly, 8Nm. I've never had and issue in 2 years and over 5000 miles.

    EDIT: The fork read 10Nm max and the bung says 8Nm.
  • gloomyandy
    gloomyandy Posts: 520
    I've used both types. The one on the right seems to be better (you actually use a smaller hex key then the one that fits the cap - at least you did on mine). An alternative used by Cervelo is to bond a short section of aluminum tube into the steerer and then use a star nut. They supply a kit of tube, epoxy, cleaner and nut to do this. Works well, but you need to get the length of the steerer right first time as you can't bond the tube and then cut it down, well not by very much. I assume they have good reason for doing it this way.
  • crikey
    crikey Posts: 362
    One important feature of bungs like this is to provide something for ham fisted spanner monkeys to tighten their stems onto; from the OP, I'd choose the one on the left...
  • Fabius
    Fabius Posts: 56
    crikey wrote:
    One important feature of bungs like this is to provide something for ham fisted spanner monkeys to tighten their stems onto; from the OP, I'd choose the one on the left...

    Thanks crikey, happy not to count myself among the many ham fisted spanner monkeys out there!
  • rafletcher
    rafletcher Posts: 1,235
    I've always used the Deda one, with carbon assembly paste. Never had any issues.

    http://www.shinybikes.com/deda-expander ... tAod2wMA3w
  • g00se
    g00se Posts: 2,221
    earth wrote:
    Keezx wrote:
    earth wrote:
    T Plus a star nut cannot be removed once fitted.

    Give me your steerer and I'll remove the starnut in 30 seconds.


    I guess they can be removed then :)


    What if some manufacturer made a steerer tube that had like a bulk head bonded into it with a thread in the centre? Effectively a bonded in bung. If they made it deep enough inside the steerer there would still be enough tube above it to allow for it to be cut to size. All you would need is a longer bolt. If the bung was carbon fibre then the absence of a metal bung would compensate for the extra weight of a longer bolt.

    Done.

    3T basically do this (Focus, Cervelo etc). The fork comes with an alloy sleeve and star nut. You cut the carbon steerer to length then epoxy the sleeve in place.

    It does limit future cutting of the fork though - A little shouldn't hurt as you could push the star-nut down a bit further into the sleeve and cut both steerer and sleeve together, but I wouldn't want to go too far.
  • Fabius
    Fabius Posts: 56
    I used the one on the right. Snugged it up nicely with the internal bolt, then set the compression with the top cap. Happy with that, nipped up the stem bolts then took the top cap off to stick the little rubber cover on the bottom bolt.

    I'll just have to make my peace with the fact that the fsa logos aren't lined up, maybe when I've finished the build I'll deal with that.

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