oldbear63

My 3 year old Fuji roadbike has had a constant problem with the headset; I have had to adjust it after every ride. Today I took it to a competent shop where the expansion nut was readjusted and the stem clamp set and it seems to be fine (though I have not taken it out yet).
This bike has a carbon steering tube and a (modern?) stem clamp. In the past I have tried disassembling the expansion nut and lightly sanding/cleaning the bearing surfaces and the inside of the steering tube and the clamp area in the past with little benefit.
How do you properly set or adjust the expansion nut and adjusting screw on a bike like this? It has disk brakes and a carbon fork.

jccaclimber

I’ve seen a lot of slipping expansion caps. Usually there’s something like the expanding section being under torqued, or being made of something unsuitable like plastic.

I’ve also seen cases where an integrated headset seat is damaged in a way that the bearing won’t sit correctly and then quickly loosens. That tends to be visible and click rather than becoming truly loose.

Things to check:
1. Headset spacers square. Same for the top and bottom of the stem, though the latter is less critical.
2. Top cap sitting on a spacer and not the steer tube or expansion plug.
3. Stem tightens properly.
4. Everything reasonably clean.
5. Everything torqued to the manufacturer’s specs, though there’s usually decent margin here.

Crankycrank

+1 to everything jccaclimber said. Also when tightening the cap make sure the stem is just loose enough to create the right tension. If the stem is too loose to the point of being able to wobble it a little it can end up slightly skewed when doing the final tightening of the stem clamp bolts causing issues with the bearing operation.