Carbon fork bung help???

The_JML
The_JML Posts: 132
edited April 2012 in Workshop
Iv just bought a 1 1/8th ritchey bung cap which is basically a bit of rubber with a top and bottom cap with the bolt going through. When the bolt is tightened the rubber expands thus pulling everything together. The problem is the bottom cap does not fit inside the steerer tube, its approx 1-2mm bigger than the inside diameter of the tube. Now the actual thickness of the carbon steerer is thicker than that of a metal steerer, so is that why it wont fit? Has anybody else had this issue and does anybody recommend a steerer bung for a carbon fork with a thick carbon steerer? thankyou

Comments

  • thel33ter
    thel33ter Posts: 2,684
    I had this problem too with a bung thing that came with my forks, so I very scientifically hammered it all into the steerer tube, tightened it up, and hoped for the best. it worked fine. Although I wouldn't really recommend it. The difference was also much smaller than 2mm.
    And now you know, and knowing is half the battle
    05 Spesh Enduro Expert
    05 Trek 1000 Custom build
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  • estampida
    estampida Posts: 1,008
    I would grease up the bung first

    no point suffering !!!
  • ugo.santalucia
    ugo.santalucia Posts: 28,301
    Sadly these expanders are all junk... The design is flawed. I have not seen one which had a convincing mechanism. The star nut is a better solution
    left the forum March 2023
  • g00se
    g00se Posts: 2,221
    The inside diameter of carbon steerers seem pretty random. Best take the fork to a local shop and see what bungs they have.

    And DONT use a start nut....
  • The_JML
    The_JML Posts: 132
    I Know not to use a star nut on a carbon steerer so that will not be happening. And as for greasing it up, its the metal bottom cap that will not fit in so grease will not work either. The rubber bung will fit in if pushed and squeezed very hard. I think i will sand the cap down until it fits in.
  • sungod
    sungod Posts: 16,851
    which ritchey bung have you got? link? pics?

    if the one you've got is just rubber, it doesn't sound right

    i've got a columbus bung in my carbon steerer, works *perfectly*...

    http://www.sjscycles.co.uk/columbus-car ... rc=froogle

    the deda one looks identical but is cheaper...

    http://www.wiggle.co.uk/deda-expander-bung/
    my bike - faster than god's and twice as shiny
  • g00se
    g00se Posts: 2,221
    The Deda one is the one I have, very good and cheap too.
  • The_JML
    The_JML Posts: 132
    Here is the pic

    http://i.imgur.com/dTJWF.jpg

    I filed the bottom ring down so it fits down inside the steerer but now the bung is too big it wont fit. It works perfect on my alloy steerer as the inside diameter is larger than my carbon one. Do i need to buy a carbon specific bung like the two mentioned above? Hope you get what i mean.
  • g00se
    g00se Posts: 2,221
    I'd go for a more 'standard' style bung for a carbon steerer - something like the deda above or if that's too long, there are slightly shorter ones.

    Some come with top caps, some don't - but I think most caps are universal fitting in terms of thread size.
  • sungod
    sungod Posts: 16,851
    The_JML wrote:
    Here is the pic

    http://i.imgur.com/dTJWF.jpg

    I filed the bottom ring down so it fits down inside the steerer but now the bung is too big it wont fit. It works perfect on my alloy steerer as the inside diameter is larger than my carbon one. Do i need to buy a carbon specific bung like the two mentioned above? Hope you get what i mean.

    doesn't look like it was made for a carbon steerer - typically a solid bung is specified by manufacturers, this provides extra internal support to the area covered by the stem clamp

    i'd get a known one like the deda
    my bike - faster than god's and twice as shiny
  • The_JML
    The_JML Posts: 132
    Ok thank. Is it common then that carbon steerers have a smaller inside diameter than alloy ones? That seems abit weird. Thanks alot guys.
  • sungod
    sungod Posts: 16,851
    not all steerers have the same wall thickness, my cf one is certainly thicker than the alloy one
    my bike - faster than god's and twice as shiny
  • Hi,

    Check out http://www.wiggle.co.uk/fsa-compressor- ... cap-th883/
    It's the same one that came with my cannondale synapse with a carbon steer. It's a bit of a fiddley job. I lost the bolt and replaced with a hope one, it didn't fit straight off: http://www.wiggle.co.uk/hope-head-doctor-expander/ it took a whole lot of adjustment and a file to get it in the steer but looks great!

    Hope it works
    Ross
  • vanleapo
    vanleapo Posts: 150
    I've had this same problem in the past.
    I just used a round file to take off a small amount of material inside the fork steerer.
    The thickness of carbon fibre does seem to vary quite a bit between manufacturers
    Tearfund Tour of Scotland 26th May to 1st June 2013
    http://www.justgiving.com/phil-godley
  • fortyone
    fortyone Posts: 166
    M Part also make a very good one.