Soo guys, the whole headset discussion here is a bit bogged down. Unfortunately, there are a lot of people here and at Hygge who have no idea about mechanics or bikes, and half-knowledge is being thrown around ("have you tried tightening it really hard?", "what if you use threadlocker?" ...).
Here is my view:
1) Hygge (or the headset manufacturer) have been quite grossly negligent here. This is a faulty design. It is impossible to achieve a play-free fit with the stiff headset cone supplied! Ever since there have been ahead headsets, they have always been made with flexible compression rings:
https://en.wikipedia.org/wiki/Headset_%28bicycle_part%292) The cone only encloses the stem to a maximum of 270deg. When braking (abutment against the lower bearing) the fork stem is pressed forwards into the opening, which is mechanically very unfavourable.
3) It is nonsense to hope that the cone supplied by Hygge can be free of play with a lot of torque on the compression bolt, loctite, high clamping torque on the stem, ....
4) Tolerances can of course play a role, but the steerer tube and taper are not designed as a press fit. A conical, flexible compression ring is required here!
Possible solutions:
- Find another suitable compression ring and replace it:
(Hygge told me that they could send me the much higher plastic ring, but that this would leave a huge gap (3mm?) between the frame and the headset cap).
I have found another cone and will explain how to install it in another post.
- Replace the entire upper headset unit:
But then you might have to rethink the connection (dovetail) to the cockpit.
Maybe this + a 3D-printed interface?
https://ritcheylogic.com/bike/headsets/Switch-upper-headset