Headset bearing - FUBAR?

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  • Was struggling with the headset of my recently acquired Arkose and so pulled the top bearing out - see picture.

    I assume its not meant to look that and so I need some new bearings?

    If I am reading it correctly (its a bit worn) the bearing has THMR 12 1 1-1/8 45 x 45 C9 on it.

    Looking online it seems to be an FSA C40 ACB headset - any tips on the best source for new bearings?

    1 Attachment

    • HS_bearing.jpg
  • That looks hella fresh compared to the bearing some people are riding about with!

  • Ha! My main concern is the bit sticking up in the middle - pretty sure that his meant to be flush with the shell.

  • That isn’t the conical wedge?

  • 45 45 1/8 bearing aka campag bearings aka the ones with the orange seal

  • You are right I took it all apart this morning, and its a sort of tapered split ring to locate the stem in the bearing.

    Having cleaned everything thoroughly, re-greased and re-assembled I'm still really struggling to tension the headset in such a way that the forks don't move under braking but not so tight that the steering is binding. Any tips from anyone?

  • Sounds like you might be missing a piece or something.

    Can you post a photo showing a sort of 'exploded' view?

  • Assuming the bearings are good (rotate smoothly when off the bike) you probably just need one or two of these under the top cover:-


  • Unfortunately I have re-assembled it without taking a picture.

    However what I have is:

    At the bottom - just the bearing; the shells are integrated to the fork/head tube

    At the top (reading up)

    • bearing
    • Split ring thing
    • 46x4 low stack headset cover (from gbj_tester)

    Above that I have a steerer tube spacer; then the stem; then another spacer; then the top cap.

  • At the bottom - just the bearing; the shells are integrated to the fork/head tube

    You don’t need a crown race on the fork?

    Could the low stack headset cover be binding against the frame?

  • The crown race is integrated to the fork.

    Re. The low stack cover - yes maybe - will look at that, might need a spacer or a slimmer cover.

  • You can get <1mm shims to go under to lift it up just enough to clear. Your lbs might have some, otherwise SJS probably has them.

  • Yep a LBS had some - a couple of super thin ones seems to have solved the problem.

    Thanks for all the help.

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Headset bearing - FUBAR?

Posted by Avatar for tertius @tertius