Expanding Bung

disgruntledgoat
disgruntledgoat Posts: 8,957
edited October 2014 in Workshop
As discussed, I'm building a bike and having a wee issue with the expanding bung in my carbon steerer forks.

If I hold the bung in my hand and tighten down, I can get the part to expand properly. On fitting to the bike, however, I can tighten up to a certain degree, but then the topcap just spins without any further tightening. How do I apply enough downward pressure to get the bung to tighten properly?
"In many ways, my story was that of a raging, Christ-like figure who hauled himself off the cross, looked up at the Romans with blood in his eyes and said 'My turn, sock cookers'"

@gietvangent

Comments

  • rrsodl
    rrsodl Posts: 486
    disgruntledgoat wrote:
    As discussed, I'm building a bike and having a wee issue with the expanding bung in my carbon steerer forks.

    If I hold the bung in my hand and tighten down, I can get the part to expand properly. On fitting to the bike, however, I can tighten up to a certain degree, but then the topcap just spins without any further tightening. How do I apply enough downward pressure to get the bung to tighten properly?

    The bung should be fitted then tighten down with the topcap off, then you can fit and tighten the topcap.
  • disgruntledgoat
    disgruntledgoat Posts: 8,957
    RRSODL wrote:
    disgruntledgoat wrote:
    As discussed, I'm building a bike and having a wee issue with the expanding bung in my carbon steerer forks.

    If I hold the bung in my hand and tighten down, I can get the part to expand properly. On fitting to the bike, however, I can tighten up to a certain degree, but then the topcap just spins without any further tightening. How do I apply enough downward pressure to get the bung to tighten properly?

    The bung should be fitted then tighten down with the topcap off, then you can fit and tighten the topcap.

    That would explain a lot.

    Thank you
    "In many ways, my story was that of a raging, Christ-like figure who hauled himself off the cross, looked up at the Romans with blood in his eyes and said 'My turn, sock cookers'"

    @gietvangent
  • Ouija
    Ouija Posts: 1,386
    You don't expand the bung with the topcap screw. It's done with the next size up allen key in the hexagonal indentations around where the top cap screw enters the bung. If you don't tighten it with that and then put the top cap and screw in all that happens is that the top cap winds the bung up the sides of the steerer tube until it touches the top cap (at which point, turning the top cap screw WILL expand the bung.... but wont be able to pull up on the steerer to preload the headset bearings as it's already as high as it can go).

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