Expander bung for carbon steerer

davidwilcock
davidwilcock Posts: 123
edited March 2014 in Workshop
Hi

I recently bought this: http://www.wiggle.co.uk/deda-expander-bung/

Unfortunatly it came with no instructions and my failsafe route of using a youtube video drew a blank.

Does anyone know how to install it?

It seems to expand when you twist it a bit

Many thanks and sorry if this is a stupidly simple question

Dave

Comments

  • BillyMansell
    BillyMansell Posts: 817
    Just drop it into the fork and tighten it up. It should sit inside and below the top of the stem and/or any spacers above the stem. You then screw the top cap bolt into the hole in the centre which will compress the headset and once there is no fork play tighten up the stem bolts.
  • davidwilcock
    davidwilcock Posts: 123
    Magic, that sounds good, thanks very much
  • mfin
    mfin Posts: 6,729
    If that one doesn't 'drop in' (deda) easily do that you can then simply tighten it you might find the inner diameter of your steerer tube is just a touch small. If this is the case so much that it becomes awkward try one by Pro instead.
  • keef66
    keef66 Posts: 13,123
    If it's anything like the one on my Scott, you'll need to tighten it up a bit first so it's a push fit into the steerer, then really tighten it when it's in.
  • on-yer-bike
    on-yer-bike Posts: 2,974
    keef66 wrote:
    If it's anything like the one on my Scott, you'll need to tighten it up a bit first so it's a push fit into the steerer, then really tighten it when it's in.
    But not too much or it might crack the carbon
    Pegoretti
    Colnago
    Cervelo
    Campagnolo
  • davidwilcock
    davidwilcock Posts: 123
    Thanks, it slotted in loosely-ish at first so i widened it a bit and pushed it in snug. Not yet screwed the top cap in but once i do, that should be fine right?
  • Ouija
    Ouija Posts: 1,386
    You'll probably need to expand the bung first before putting the top cap anywhere near it (the top cap screw isn't used to expand the bung). Look at the hole in the bung where the top cap bolt goes into it and you'll see a hex hole depression around the sides of it where you put an allen key to expand the bung. After doing that so that the bung is very firmly gripping the sides of the steerer tube then put the top cap on and tighten it up to preload the bearings .

    Failure to do it in that order will simply cause the top cap screw to pull the bung up the steerer tube until it touches the top cap. And then it'll expand, so that the top cap is applying no pressure to the bearings (which isn't what you want).
  • raymondliu
    raymondliu Posts: 56
    Hijacking the thread a bit but does anyone have experience with this product http://www.chainreactioncycles.com/bran ... -prod95405
  • BillyMansell
    BillyMansell Posts: 817
    raymondliu wrote:
    Hijacking the thread a bit but does anyone have experience with this product http://www.chainreactioncycles.com/bran ... -prod95405
    Interesting idea. They've combined the expander bolt and preload bolt into one.

    My only concern would be in ensuring the location of the expander inside the steerer was ideally placed to spread the load of the stem bolts. This could be done by screwing in the bolt to the required depth before inserting which could be a bit hit and miss and I suspect some people may just drop it in and tighten it up without thinking about spreading the load of the stem on the steerer.
  • balthazar
    balthazar Posts: 1,565
    raymondliu wrote:
    Hijacking the thread a bit but does anyone have experience with this product http://www.chainreactioncycles.com/bran ... -prod95405

    I wouldn't. I don't see any benefit, but I do see potential cost in something that looks tricksy to use. Lightly fixing a threaded bung in a steerer tube is an easy design challenge, well solved by everyone else. If you can't set headset preload properly with this you won't know whether the bung is slipping, or some other problem.

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