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I recently bought a second hand BMC teammachine 2016(?). The frame looked in really good condition. Back home I started the build by servicing the headset. Af purchase time the stem was off the fork, and I did not ask why, I assumed because of transportation. I cleaned, tested the bearings and they felt very smooth, so I put it back together with new grease. At the step of ajusting the preload by tightening/loosening the top cap I could not get the right amount: or there was play, or it was too tight and rubbing (the headset cover would not turn with the fork, same for the spacers , unlike the stem which would turn). I first thought I had put the bearings the wrong way around, but I can rules this out now.

I dismantled my commuter road bike, which headset I have serviced successfully in the past, and noticed that the only difference is that it has a compression ring (metal ring with an opening) between the top bearing and the headset cover.

Is that what I am missing here? Is it possible for the BMC headset to come without the compression ring?

Here are some pictures of all pieces making the headset, as I've bought it. The compression plug is inside the steerer tube, it is fitting there snug if it matters. Also I have run my finger through the headset bearings cups on the frame and they feel very smooth to me.

enter image description here

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  • looks like i have the same issue with slr03 2021. The headset is too loose for me compare to my previous bike and i cannot adjust it with top cap bolt... Have you resolved it?
    – Anton K
    Commented Sep 3, 2023 at 22:17
  • @AntonK yeah, in my case I was missing a compression ring. I talked to the chap who sold me the frame second hand and he found the right piece in his workshop. Adjusting the right payload with that piece was straightforward.
    – Learning is a mess
    Commented Nov 6, 2023 at 23:14

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As far as I understand headsets, you identified the issue correctly. In your case, you apply preload over spacers and stem unto the dust cover. Without the compression ring, the dust cover presses unto the outer part of the upper bearing instead of the inner ring. This cant't work and will probably damage the sealing ring attached to the dust cover. I don't think the BMC headsets should come without a compression ring. Googled 'BMC headset' and few schematic drawings of bikes popped up, all of them with compression rings. I don't know if those rings are sold seperately. You probably need a new headset.

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  • Thanks for the input. Do you think this compression ring is proprietary? Or can I use one from a spare bike in the meantime?
    – Learning is a mess
    Commented Oct 28, 2022 at 15:25
  • Sorry for the late answer. I have never thought about taking compression rings from different headset. This will probably work in some cases, although it may depend on bearing and dust cap. Maybe just try it with some cheap compression ring that can be bought separately?
    – reciprocal lettuce
    Commented Nov 7, 2022 at 9:17
  • Late comeback, the seller got me a compatible compression ring and I manage to assemble the headset. It brought me a great pleasure to steer the stem without hearing carbon on carbon rubbing!
    – Learning is a mess
    Commented Nov 23, 2023 at 17:17

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