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1" threaded headset replacement

ChrisSAChrisSA Posts: 455
edited February 2011 in Workshop
Current headset needs replacing, due to false brinelling in the cups.

What is the impact of the stack height of the threaded headset? Is there any issue with the threaded part sticking out of the lock nut, or is the lock nut traditionally domed such that the fork cannot poke through?

The other option is to replace the steel fork with a carbon threadless one - though I understand that there may not be such a weight saving due to alloy steerer....

Posts

  • Not sure what false brinelling is. But my dentist said I had it.

    If you know the make/model of your old headset you might be able to find the stack height on the internet.

    Get a headset with a stack height lower than your old one and that is no huge problem. You just cut some more off the length of the steerer. This operation will require the correct tools though and a certain amount of know-how.

    Get one with a stack height too high and you will not be able to use it because the steerer tube will not be long enough for the locknut to actually screw on to it.
  • andrew_sandrew_s Posts: 2,511
    The locknut generally won't allow an over long steerer to poke through.
    You'd normally put a spacer/washer between the cup and the locknut, which should be keyed to a groove in the back of the steerer to stop it rotating. Any un-keyed spacers should go below the keyed spacer.

    Brinelling is where an impact between 2 objects leaves a dent in the softer.
    In a worn bike headset you get indentations where the balls sit in the straight ahead position, which leads to self-centring steering as the balls drop into the indentations.
    This is often called brinelling, but it isn't as the indentations are caused by fretting rather than impact.
    The grease gets squeezed out from between the ball and the race, and there isn't enough movement in the headset of a bicycle being ridden in a straight line to replenish it. With no grease, the microscopic bumps on the ball pressure weld to those on the race, and subsequent movement tears the weld apart. Over time enough material gets removed to leave the dent.
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