Why do headsets go out of adjustment?

[Sergeant Pluck]

I've had my Van Nicholas audax bike for maybe 18 months now. Great bike, no problems with it at all.

I've only had to adjust the headset twice. The first time was after I'd gone into a sharp-edged pothole hidden by a puddle - quite a hard impact, tyre punctured but the wheel was fine. The headset was a tiny bit loose after this. Being a paranoid sort, I took the fork out for a good look at it prior to adjusting it.

This morning I noted that the headset was a little bit out. I rode the bike for 70 km or so and when I checked it after the ride it was a little looser. Nothing major; adjusted it back up easily and it is fine now.

Should I take the fork out again and re-check?? Or is it normal to have to adjust it once in a while? The stem is tightened properly so movement there cannot be the source. The only other possibilities I can think of are that (1) the knocks have squeezed out the small amount of grease used around the bearings in the headset or (2) there has been a little movement in the carbon spacers under the stem.

Are (1) and (2) the likely culprits?

[Biggsy]

(1) may be part of it.  (2) doesn't make a difference if the stem doesn't move.

I suspect the stem does move even when you think it's properly tight.  I've had the same problem as well and can't work out what else it can be in my case besides stem movement.  Don't worry about the forks yet.

[Sergeant Pluck]

(1) may be part of it.  (2) doesn't make a difference if the stem doesn't move.

Thanks Biggsy. But let's say the carbon spacers are not that well faced together - surely over time they could be forced closer together against the (fixed) stem, thereby causing looseness?

[Biggsy]

That's a good theory.  Try to remove the play by rotating the spacers (relative to each other, without loosening the stem).  If that's not possible then the stem (or something else) must have shifted.

[Sergeant Pluck]

They could not be turned at any stage.

I guess my main worry is that this might be a symptom of some more significant problem with the steerer. But if it is normal to have the headset go a little out of adjustment every 6 months or a year then that's OK.

[kyuss]

Are you using a star nut or a steerer bung? Star nuts are pretty reliable but I've found on the bike with a steerer bung that it can sometimes slip up the steerer after a big impact. I think it is just not getting enough purchase on the inside of the steerer tube. It's fine in normal riding but can slip after a hard knock. I guess it shouldn't matter if the stem is tightened properly but it seems to.

[Simon Galgut]

With my experience of alloy steerers (esp. on VN bikes) I would now be binning the forks and replacing them with some nice reliable steel ones 

[andygates]

A slipping nut or bung shouldn't be a problem in regular use, though; once the stem is tightened down, you can remove the top-cap and bolt entirely if you like (it's scary seeing the wheel and road through it!). 

[Sergeant Pluck]

Are you using a star nut or a steerer bung?

Star nut on this bike. (I found a bung to be a better job, TBH, on a fork with a steel steerer on my Marin: perhaps the internal diameter of the steel fork was larger than than a star nut was intended for).

A slipping nut or bung shouldn't be a problem in regular use

I'm pretty sure the SFN has not moved. Hence my slight perturbation as to where the looseness has come from.

With my experience of alloy steerers (esp. on VN bikes) I would now be binning the forks and replacing them with some nice reliable steel ones

Can you scare me in more detail please?

Slightly OT, I note that the options for good all carbon forks with mudguard eyes are still very limited. And when are we going to see some good titanium forks? Or perhaps carbon forks with titanium steerers? I know Colnago do a carbon and (partly) titanium fork but I don't know of any others.

[border-rider]

With my experience of alloy steerers (esp. on VN bikes) I would now be binning the forks and replacing them with some nice reliable steel ones 

I have to say, I'd be working hard to find out what's going on

if the stem's not moving up (why would it ?) and the spacers are not distorting in some way, there's no reason at all for routine loosening of the headset.  i don't touch mine for years, sometimes.

I hope that it doesn't apply to you, but as Simon implied a regularly-loosening headset can be the first symptom of incipient alloy steerer failure.

[andygates]

if the stem's not moving up (why would it ?)

The original impact.  Possibly. If the stem was twisted in the fall, it surely can be twisted up.

The second looseness then comes down to a more mundane "ur doin it wrong" after the first fix, Sarge - easy to do by overpacking the bearings (as you identified) or just getting it wrong.  I often err on the side of loose for fear of overtightening, and then have to tighten it up later.

[Hummers]

My headset seems to have developed a 'notch'.

Is this a common thing?

I've not noticed it on other bikes.

H

[Sergeant Pluck]

if the stem's not moving up (why would it ?) and the spacers are not distorting in some way, there's no reason at all for routine loosening of the headset

Hence my queries. It's not routine though - as I say it loosened off once after a hard impact, and was then fine until today. I did repack the headset after the first episode so perhaps I was too generous with the assembly grease.

Looks as if I'll have to take it out for another look  

What I'd like to do is to replace the fork at some point, preferably with one that does not have an alloy steerer, but I can't see anything available with mudguard eyes that convinces me. Any suggestions?

Easton do a strong looking all-carbon cyclocross fork which does have mudguard eyes and appears to be drilled for a brake, despite the presence of V-brake mounts, but that is probably overkill.

[andygates]

My headset seems to have developed a 'notch'.

Is this a common thing?

Yes, it means it's buggered.  And not in the fun sense.  It's been either loose or tight or dry or abused, and the bearing surfaces have become pitted where the bearings sit.  Replacement is the solution; taking the bearing cups out of the frame, rotating them and re-seating is a workaround (it moves the notch to where you never feel it) but for the faff, most people just replace.

[scampi]

My headset seems to have developed a 'notch'.
...

If this is the problem I think it is, I think over time the ball bearings can indent a dotted pattern in the race so they sit in the dents and the steering then settles into certain positions rather than rotating smoothly.

I have had this happen before and decided it was time to change the headset but according to Sheldon Brown the problem can be overcome by removing the ball bearings along with the little guide that keeps them in place, and replacing just with ball bearings.

Therefore there are more ball bearings in there than before, so they don't fall into the previous grooves.

[Biggsy]

I don't know how stems can slip upwards (Stem not clamped well enough?  Bumps & vibration?  Pulling up on the bars?), but sometmes after inspecting everything there's just no other explanation other than that the stem has moved.

There's a recent thread on the subject on rec.bicycles.tech if you want to read more theories and stuff: "Perpetually loosening threadless headset..."

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Changing from caged to loose balls only helps for a short while, IME, before it gets notchy again.

I would change the headset for one with cartridge bearings.