Carbon fork steerer, expanding bung, what torque (Nm) to tighten ?

Discussion in 'Cycling Equipment' started by Fradbut, Dec 20, 2005.

  1. Fradbut

    Fradbut New Member

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    When tightening the expandable bung inside a carbon steerer what is the reccomended torque setting (Nm) to tighten the bung enough to fix it but not too much too damage the steerer ? Anyone know ?
     
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  2. mjmc1273

    mjmc1273 New Member

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    It very much depends on the manufactor, but the Specialized people say to set the expanion plug to (5.6 Nm) and not to exceed maximum torque of 6.8 Nm. The plug really only needs to be tight enough not to move up or down the steerer tube when setting the bearings with the top cap hex nut adjustment. Good luck :)
     
  3. fish156

    fish156 New Member

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    With a star nut, when you tighten it up you are establishing the pre-load on the headset bearings (and then you lock this load by tightenning the stem). I believe (but, I'm not positive) that expandable bungs accomplish the same, in addition to gripping the inside of the steerer tube.

    So, what you really need to find out is what the specification for the pre-load is for your headset bearings. This is going to be more important than what stress the inside of the steerer tube will take, as the bearing spec is almost certainly going to be much less than what's safe for the steerer tube. Contact your headset manufacturer for the correct bearing pre-loading tension.

    The important spec for the steerer tube will be how tight you can make the binder bolts on the stem.

    Park has a nice chart with torque specs. Conversion formulae are on pg 5:

    http://www.parktool.com/repair/howtos/torque.pdf

    Here is an example for Cane Creek headsets and there are some pertinent comments about the ramifications of incorrect pre-loading(see Section C, item 5):

    http://www.canecreek.com/fileadmin/canecreek/products/headsets/man_cc_head/c2_headset_eng.pdf
     
  4. Fradbut

    Fradbut New Member

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    Thanks - most helpful
     
  5. Fradbut

    Fradbut New Member

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    Hi - The Richey site tells me to tighten the stem handlebar bolts to 5Nm but what of the stem steerer bolts ? I'm tightening onto a carbon steerer and I know that they all vary in thickness but I can't find any information on torque recommendations. Any ideas ?
     
  6. Fradbut

    Fradbut New Member

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    Hi - The Richey site tells me to tighten the stem handlebar bolts to 5Nm but what of the stem steerer bolts ? I'm tightening onto a carbon steerer and I know that they all vary in thickness but I can't find any information on torque recommendations. Any ideas ?
     
  7. alienator

    alienator Well-Known Member

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    5nm.....it's not printed on yer stem?
     
  8. Fradbut

    Fradbut New Member

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    not on the standard size but maybe on the OS
     
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