Headset / Stem Knock

Dizeee
Dizeee Posts: 337
edited December 2013 in Workshop
As per usual and on queue, my 2012 Trek FX7 has developed another knock from the stem, which is quite pronounced upon rocking the bike with front brake on.

Being the technophobe I am I attempted just now to unscrew the allam nut to tighten it. This nut is NOT moving, if i turn my multi tool any harder it is going to shear / break.

Do I need to use a spanner on the hexaganol thing first or am I doing the right thing? Also how to move this allam screw?

Comments

  • majormantra
    majormantra Posts: 2,094
    Google headset adjustment and learn the difference between a quill stem and an a-head stem.

    You don't specify exactly which model you have (e.g. 7.3 FX) but if it's one of the ones with a quill stem then you would need headset spanners or one headset spanner plus an adjustable. The bolt on top of a quill stem holds the stem in place and is NOT an adjustment.

    If it's an a-head stem then adjustment is carried out by loosening the pinch (side) bolts and then adjust the preload (top) bolt.

    If none of that makes sense then take your bike to a shop. It's a 30 second job done right. Do it wrong and you may endanger yourself.
  • farrina
    farrina Posts: 360
    Try the oracle here http://sheldonbrown.com/headsets.html which has some pictures to show the two types.
    If its a threaded headset (the older type) as previously advised) you will need a set of headset spanners.
    Regards

    Alan
    Regards
    Alan
  • keef66
    keef66 Posts: 13,123
    If it's a 2012 bike it will be an ahead stem. Loosen the 2 clamp bolts that secure the stem to the steerer first, then see if you can move the bolt in the middle of the cap.

    If so, tighten the cap bolt a tiny bit (quarter of a turn), nip up the clamp bolts and see if that's reduced the knocking when you apply the front brake and rock back and forth. Repeat until you've eliminated the play.

    If you cannot eliminate the knocking or you've had to tighten so much the steering is now stiff, it's possible the headset bearings are knackered, or possibly the star nut or bung which the cap bolt threads into has moved up and needs repositioning.
  • majormantra
    majormantra Posts: 2,094
    keef66 wrote:
    If it's a 2012 bike it will be an ahead stem.

    Plenty of entry level bikes including the cheaper Treks have quill stems.
  • keef66
    keef66 Posts: 13,123
    MajorMantra wrote:
    keef66 wrote:
    If it's a 2012 bike it will be an ahead stem.

    Plenty of entry level bikes including the cheaper Treks have quill stems.

    Well you live and learn!

    OK, after checking on Sheldon Brown, feel free to disregard the advice above if it turns out you have a quill stem.
  • Dizeee
    Dizeee Posts: 337
    Its a quill...

    Its a 7.0 FX.

    Will a spanner do and do I adjust that first?
  • keef66
    keef66 Posts: 13,123
    OK, if it's a quill stem you should leave the nut on top well alone unless you want to adjust the handlebar height.

    Instead, to tighten up the headset you need to tackle the big hexagonal / octagonal things above the upper headset bearing. I'm guessing the lockring isn't doing it's job and the whole thing's coming loose.

    have a look on Park Tools

    http://www.parktool.com/blog/repair-hel ... et-service
  • majormantra
    majormantra Posts: 2,094
    You'll struggle without at least one proper headset spanner, you need to be able to hold the lower nut as you tighten the upper locknut.

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