Carbon Steerer Headset Bung

Leadballoon
Leadballoon Posts: 31
edited April 2013 in Workshop
I've almost completed my R872 build but one thing doesn't quite make sense. As the fork has a carbon steerer I bought an expanding bung (M-PART) but I don't understand how this "pre-loads". With a star nut, the effect of tightening the allen nut draws the fork steerer up, removing any play. The single nut on the M-Part bung works the expansion but by the time it is "biting" on the inside of the steerer I don't see how it can then continue to be tightened to pre load the headset.

I hope this is clear and someone can let me know what I "just don't get".

Thanks

Comments

  • sungod
    sungod Posts: 17,496
    not familiar with that bung, but usually they are fitted like this...

    remove the bolt

    the recess that the bolt goes into usually takes a hex key

    put bung in steerer, use hex key to expand it so that it won't slip

    now put the top cap on and screw in the bolt to set preload
    my bike - faster than god's and twice as shiny
  • g00se
    g00se Posts: 2,221
    Yup,

    The internally threaded centre of the bung takes a large allen key - this forces the outside of the bung out and tightens it up against the inside of the steerer. Once tight, remove the allen key and there is a smaller threaded hole through the centre (inside the recess for the allen key).
  • Leadballoon
    Leadballoon Posts: 31
    Thank you, I knew it would have to be down to my inability to work it out. It was so frustrating to go through everything, making a bearing press for the BB and working out the internal cabling to fall at the last hurdle.

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