Handlebars won't steer front wheel - still salvageable?

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Ruadh495
Posts: 413
Joined: 25 Jun 2016, 11:10am

Re: Handlebars won't steer front wheel - still salvageable?

Post by Ruadh495 »

Looks to me like the wedge is the wrong way round, so it's not locking the stem in the steerer. The sloped side of the wedge should match the slope on the bottom of the stem.
reohn2
Posts: 45158
Joined: 26 Jun 2009, 8:21pm

Re: Handlebars won't steer front wheel - still salvageable?

Post by reohn2 »

Ruadh495 wrote:Looks to me like the wedge is the wrong way round, so it's not locking the stem in the steerer. The sloped side of the wedge should match the slope on the bottom of the stem.

I don't think it's that bad,the bolt isn't long enough to allow the wedge to twist around.
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Ruadh495
Posts: 413
Joined: 25 Jun 2016, 11:10am

Re: Handlebars won't steer front wheel - still salvageable?

Post by Ruadh495 »

It looks like it's been put on the wrong way round, with the flat side towards the stem rather than the sloped one. I'm not quite sure from the picture, though, and I'm surprised the bolt is long enough as well.
alexnharvey
Posts: 1923
Joined: 10 Jan 2014, 8:39am

Re: Handlebars won't steer front wheel - still salvageable?

Post by alexnharvey »

Ruadh495 wrote:It looks like it's been put on the wrong way round, with the flat side towards the stem rather than the sloped one. I'm not quite sure from the picture, though, and I'm surprised the bolt is long enough as well.


It looks the right way round to me, angle to angle, flat on the bottom.
reohn2
Posts: 45158
Joined: 26 Jun 2009, 8:21pm

Re: Handlebars won't steer front wheel - still salvageable?

Post by reohn2 »

alexnharvey wrote:
Ruadh495 wrote:It looks like it's been put on the wrong way round, with the flat side towards the stem rather than the sloped one. I'm not quite sure from the picture, though, and I'm surprised the bolt is long enough as well.


It looks the right way round to me, angle to angle, flat on the bottom.


+1
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"All we are not stares back at what we are"
W H Auden
aljohn
Posts: 59
Joined: 7 Sep 2012, 9:39pm

Re: Handlebars won't steer front wheel - still salvageable?

Post by aljohn »

Back in the 50's and 60's I had several bikes with both types of quill stems and never had a problem with them. However, in 2007 at a flea market,rastro, in Spain I bought an Italian Somec.it was a little tatty and I took it home and rebuilt it. The stem had the circular , internal wedge. This worked fine until one day after coming down a steep, windy road I stopped for a coffee. As I wheeled the bike the front wheel moved sideways on its own. I couldn't believe that I'd been cornering at speed an hour earlier on this bike. I tried tightening the stem but it was not that successful. It was a very slow ride back. when I took it apart the inside of the fork tube and the stem where they had been locked were very shiny and the base of the stem had a slight bulge. I cured it by fitting a new stem with the sliding wedge type - the wedge was fluted. This really gripped the fork tube and I had no more problems with it. I always liked the neatness of the circular, internal wedge, but I would always use the sliding, external wedge now.
Brucey
Posts: 44516
Joined: 4 Jan 2012, 6:25pm

Re: Handlebars won't steer front wheel - still salvageable?

Post by Brucey »

aljohn wrote: I tried tightening the stem but it was not that successful. It was a very slow ride back. when I took it apart the inside of the fork tube and the stem where they had been locked were very shiny and the base of the stem had a slight bulge. I cured it by fitting a new stem ...


IME this can happen if a conical wedge is

a) allowed to drop below the end of the stem and/or

b) the retaining tab (if present) doesn't engage with the slot or

c) the conical wedge is installed the wrong way up.

The result is that when the bolt is tightened, instead of the wedge entering the end of the stem, the flat parts of the wedge can bear against the end of the stem, and if the stem grips at all, it'll do so by bulging as you describe. The bulge is usually about 1/2" to 1" above the bottom of the stem. You were quite right to be concerned; the grip is almost non-existent this way.

If you use a conical wedge stem and you wish to avoid this kind of trouble;

- always make sure that the conical wedge is engaged properly with the stem before fitting it to the steerer
- when adjusting the stem, always be sure to undo the bolt by no more than two turns (as almost invariably specified in the instructions for this kind of stem) so that the conical wedge can't go too low
- develop a feel for how the bolt is tightening; a conical wedge usually takes about one full turn (from first real resistance) to go fully tight
- check that the wedge is, er 'wedged' properly by undoing the bolt two turns and then trying to move the handlebars; if the wedge is correctly installed, the handlebars won't move easily even with the bolt slack. NB the bolt head needs to tapped down to release a wedge of this type.

in point of fact I think that conical wedges are arguably superior to the modern type; I think they grip better and are kinder to the steerer tube. Because the wedge angle is smaller, and the bolt usually has a finer pitch to it, they provide more grip for any given bolt torque, and should the bolt work loose, the wedge usually remains secure (unlike the modern type). Because the bolt tension can be lower, you can more easily make a really lightweight conical expander assembly.

The modern sort are cheaper to make (by far) and are less easy to misassemble. But past that I don't think they have any real advantages...?

cheers
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