Loose Steering / Threaded Headset

[ruffstuffbadger]

If I stand with the front wheel trapped between my legs, facing toward the back of the back, I can tighten the expander bolt(?) [the one that runs down inside the stem and is accessible from above]. If I then try to turn the handlebars counter clockwise, with the wheel still trapped, they remain tight (as I imagine they should), but when I try to turn them clockwise they come loose with very little effort. I assume that shouldn't happen.

If it shouldn't happen what might be the cause? As I say, the bolt tightens down firmly so it doesn't seem to be a problem with worn threads.

Just before I noticed this happening, I had had the headset serviced at a bike store. Could they have put something back in the wrong place?

I want to find out what the cause might be before taking it back to them, as I imagine they would deny any failing on their part unless I could prove otherwise. I have considered first taking it to a different bike store, but thought I would check here first, especially as I'll be paying extra at a second bike store when the problem might have nothing to do with the previous service or might not even be a problem.

[james01]

This certainly shouldn't be happening. First, I would obviously try tightening the bolt as much as possible (although you've probably already done this).
Secondly I would slacken the bolt a few turns, then tap it with a light hammer to ensure that the wedge-shaped nut below is no longer jamming the stem. Withdraw the stem from the steerer tube with handlebars still attached - this sometimes needs a bit of wiggling. Inspect the long bolt where it enters the wedge shaped nut. Is there plenty of thread-length available when it is tightened? Is the thread damaged in some way, thus preventing you from tightening fully? Another possibility is that the wedge-nut and stem are not compatible, having been mixed up in a previous maintenance session. Don't risk riding the bike until fixed.

[531colin]

I agree with James above, take the stem out as he describes and look at it (even, post a photo on here)
I would do that without first using violence on the expander bolt .

[ruffstuffbadger]

Hi James and Colin,

I easily removed the stem without having to tap anything with a hammer, and could find no wear or damage to the threads of the bolt or the wedge, and there is a centimetre or two of bolt extending from the wedge. I wonder if the wedge is just too small for the tube, hence the ease with which it was withdrawn, though I hadn't noticed this problem in previous years. As it's beyond my skill level I'll take it to the bike shop. Thanks for your help.

[531colin]

I'm guessing its a wedge at about 45 degrees angle with a matching angle on the bottom of the stem?
The grip to the inside of the steerer tube comes from the 2 wedges working against each other, so the size of the stem "grows".
Seems like a lot of thread sticking out the bottom of the wedge, are you sure when you tighten the bolt it is actually tightening the wedge, not just hitting the end of the thread? You can test this by putting a washer or two (or even a nut if a suitable one comes to hand) under the head of the expander bolt and trying it in the bike, or even out of the bike just seeing if the bolt will pull the wedge up so that its obviously too high, ie the stem and wedge are too "fat" to go into the steerer tube.
Before you do that, take the bolt right out (again!) and look at the mating faces of the wedge and the stem.....they need to slide against each other, when there is quite a bit of pressure holding them together, so they need to be fairly smooth and clean (not rusty, etc.) and they need to be greased.
Its a fairly simple system, there is little to go wrong, really. .....although I have seen a steerer tube distorted by some lunatic hammering the top of the stem to try to get the bars lower than they could physically go.....the stem and expander wedge had made a matching bulge in the bottom of the steerer tube, above where it is internally butted for strength....ie. the tube wall is thicker, and the hole in the middle smaller, which stops the stem going down any further.
I think you are nearly there!

[ruffstuffbadger]

Thanks Colin, I'll try your suggestions tomorrow in the daylight.

[sreten]

Hi,

As it has occurred since your headset change the LBS should be willing to analyse the
problem rather than fob you off. They should be interested in what is wrong with a bike
they let out of the door that isn't as safe as it should be, they should know more than
you and they have customers who know far less than you, who don't check anything.

I suspect the the stem is being re-installed too far down, hitting a taper in the
bottom of the headtube and preventing the stem and wedge seating properly.
Can't think of another reason why the highly reliable arrangement won't work.

rgds, sreten.

[ruffstuffbadger]

Thanks sreten. I'll do one more check following Colin's suggestions and bearing yours in mind and, if it doesn't solve the problem, then it's back to the bike shop.

[ruffstuffbadger]

Fixed! Thanks for all your help.

[531colin]

Fixed! Thanks for all your help.

So what was wrong?

[ruffstuffbadger]

So what was wrong?

I don't know Colin. I made sure the surfaces were greased and repositioned the stem a little higher and it didn't work, then I took it out, screwed the wedge a little further up the expander bolt, repositioned it again and it worked! I'm guessing that the wedge had been lower down the expander bolt when the stem was inserted at the bike store and wasn't being brought into close enough contact with the stem. But then shouldn't the wedge rise up the bolt as it is tightened to meet the stem making its original position irrelevant?

[531colin]

Beats me.....its a wedge working in a tube just a bit bigger.....what can go wrong?.....

[Brucey]

steerer tubes are often internally butted. I have known a wedge bolt jam in the butt at the wrong angle, and then not tighten up correctly in the way described, so it might have been that.

cheers

[ruffstuffbadger]

I have a headlight mounted on the steering tube, where the front mudguard would attach, secured by a bolt running right through. I wonder if the expander bolt was hitting that and, if the wedge was too low down the bolt when the stem was insterted, wasn't rising enough to meet the stem as the bolt wasn't actually descending any further.