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Slipping steerer bung

paulbnixpaulbnix Posts: 466
My new Px bike came with one of these https://www.planetx.co.uk/i/q/FSPXFBUMK2/planet-x-carbon-steerer-fork-bung-mk-2.

I am having difficulty stopping it moving when I apply the preload with top bolt.
Sometimes I can get it to hold with approx 10nm on my cheap torque wrench but it takes a number of tries.

I have tried adding carbon assembly paste but it didn't seem to make any difference.

Would a different bung help? Any suggestions?

Thanks

Posts

  • N0bodyOfTheGoatN0bodyOfTheGoat Posts: 4,006
    Have you tried tightening the internal hex bolt that expands the bung? If this is loose and you tighten the topcap bolt, the bung will be pulled out of the head tube.
    ================
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  • paulbnixpaulbnix Posts: 466
    That’s exactly what I have done.
    I feel I’m tightening the internal bolt far too much before the bung stops twisting when I apply preload.
    Just wondered if there is a more grippy bung.
  • Its possible the bung does not fit the steer properly but more likely you just ha e not tightened it enough.those brings ha e to be nice and tight not to slip. Some.bungs are better than others though. There only two I use know on account of the others being censored .
  • paulbnixpaulbnix Posts: 466

    There only two I use know on account of the others being censored .

    And the two you use are?
  • arlowoodarlowood Posts: 2,378
    edited 16 March
    I'm guessing this is probably one of them since it is available on Malcolm's website.

    https://thecycleclinic.co.uk/collections/headsets/products/zenith-carbon-fork-bung-for-1-1-8-steerer-tubes




    I bought one a couple of years back for a PX Pro Carbon build and it worked fine. No slipping or installation problems
  • paulbnixpaulbnix Posts: 466
    I ordered one from Cycleclinic and have just fitted it and it is holding much better.

    The Px one had a cone at the bottom that only pushed the lower section of the bung apart.

    The new one has a cone at top and bottom so pushes the whole centre section of the bung apart giving much more contact area with the steeerer.

    I’ve successfully used the Px bung on other bikes - maybe the inner surface of the steerer was different in some way.
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