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The headset on my TT bike is a bit of a mystery - front end of a TT bike sees some tinkering, and I can never get the headset done back up again, yet the LBS mechanic can do it trivially (and refuses to disclose his observations, wise man).
You're probably thinking TT bike - must be some complicated non-standard bollox, but no! It is a standard conventional (carbon) fork, and the headset is very simple. Crown race and lower bearing, then upper bearing, collar, and top cap (pictured). Any ideas on what I'm missing here, key components to jiggle - before I bring it back in (again)?
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Is the top cap bottoming on the top of the steerer? You need a few mms clearance to allow it to preload the bearings.
Have you tried fitting a small spacer under that dust shield. It looks like it might be contacting the frame, in which case it could prevent the bearings from being preloaded.
Thks thols, the top cap is sound, but it could well be something up with how I'm preloading the top bearing.
Thing is it has been completely solid up to now on this exact headset, so it is defo an assembly problem and not something missing or out of spec with the component.
I want to know more about the rust and the resulting lifting paint.
Considering how much rust there is on that bearing race, are you sure that the bearing hasn't now collapsed and resulting in it knocking and feeling like a loose headset?
With stuff like this, it's often a good idea to pull the whole thing apart and reassemble it, checking it after each step. If you remove that dust cover and just assemble it with normal spacers under the stem, does it tighten up properly? If the bearings are preloaded and it still has movement, then there must be some problem with the bearings themselves.
Pop an extra spacer in and just try it.
Either that or the fork bung isn’t tight.
This has solved it when it happened to me twice.
+1 on extra spacer
What BearBack said - that’s a mess.
Is it that the top cap has a rubber seal in it that's catching on the steerer? I had a headset that was similar and a bit of silicone lube on the o ring helped it slide down
Without seeing it with the stem on and top cap off it's hard to judge.
It Def sounds like something is bottoming out.
That bearing looks a state, I would remove the bearing to see what it is like. The bottom bearing could be even worse as water gets into it from the front tyre.
Thks for all the advice - I've sorted it out by playing with spacers as suggested and it was the bung not sitting quite right.
There's some sort of raised imperfection down the steerer I could feel with the digits - bung assembly was sitting flush so I thought it was OK, but I guess the expanding bit (three 120 degree wedge type) was being interfered with. An extra spacer up top has tightened it all up.