Can't Flip Stem?

Jezston

Über Member
Location
London
This is odd. Tried to flip the stem on my Kona Dew Plus last night to get my butchered bullhorns into a more 'racey' position, but I'm unable to get it back on tight enough without the handlebars coming loose and moving independently of the front wheel, which obviously makes it unridable.

Not sure what the technical term for it, but the fork ... err ... tube thing doesn't have a thread or anything like that - the handlebar stem is adjustable using spacers, then screws tight with two screws, and a long screw that goes down the tube from the top.

Took the stem off last night, took handlebars off stem, turned it upside down so it's pointing slightly downwards rather than slightly upwards, put the spacers back on, screwed everything in, put handlebars back on, seems ok, soon as a I start moving, the handlebars move independently of the front wheel. Tried tightening it up like a b*stard but no joy - turn the wheel right seems to unscrew the ... err ... 'vertical' screw down the ... err. ... tube thing.

Worried I'd broken something, I put everything back on the way it was before - and it's fine. Hardly needed to screw it up nearly as tight.

Is this right? I thought with this type of stem it could be flipped whatever which way and be fine. Chap at the LBS I phoned up seemed to think it was very odd too. Any ideas?
 
If tightening of the headset is done in the wrong order no amount of tightening will do any good in fact it may do damage. When done in the right order its surprising how little force is needed. IIRC with everything loose you tighten the two bolts on the side of the clamp first and then tighten the stem bolt on the top. Check whether or not this is the right order though I think bicycle tutor has a video.

Edit its the other way you adjust with the stem bolt and then fix with the two clamp bolts.
 

g00se

Veteran
Location
Norwich
There shouldn't be any issues flipping the stem on that bike - I've got the same one and flipped it over a while back.

Just want to make sure you know how a threadless headset works - sorry if I'm teaching you to suck eggs:

The bottom bearings are held under the correct pressure by the forks being pulled up. The top bearing are held under pressure of the STEM and spacers pushing down. To get this to work, the stem has to be pushed down the steerer to the correct pressure then clamped onto the steerer.

This is a bit tricky to do, so the top cap is used as an aid while the stem is loose. It applies the pressure and can be adjusted until the presure is just right (no lateral movement of the fork but free to rotate) and at that point, the stem's pinch bolts can be tightened to make the whole thing secure.

Once the stem is tight, the top cap and bolt are effectively just a dust cover :smile:

Does that help in any way?
 

accountantpete

Brexiteer
You are not going to break anything so give it another go.

Presumably the fork tube (called a steerer) is alloy.

Undo and take off the top cap (the long screw) and loosen the two bolts attaching the stem to the steerer - you can then remove the stem and turn it the way you want.

Then with everything in place and the bars/forks roughly straight, insert and tighten up the top cap only until any play in the forks disappears but the forks turn freely without judder..

Once happy, position the stem/bars correctly and tighten up the two bolts attaching the stem to the steerer..

You should then be able to loosen the top cap off as the stem/steerer bolts do all the work and the top-cap is there mainly for the initial adjustment and to keep the water out.
 
OP
Jezston

Jezston

Über Member
Location
London
See I did this twice yesterday, once before leaving work, and once when I got home, and pretty sure I followed the procedure outlined by Pete above on my second attempt, and yet still it would not stay secure flipped but was absolutely fine, no matter what order I tightened what, when turned back round again.

I'll give it another go lunchtime. Is there something I could have done to the bike that'll be stopping it working as it should?
 

g00se

Veteran
Location
Norwich
Are you keeping the spacers below (between the stem and the head tube) or are you putting these above the steerer too?
 
OP
Jezston

Jezston

Über Member
Location
London
Just tried it again, making sure I followed the instructions. Same problem.

It seems that turning the wheel with the stem inverted is unscrewing the top cap - I can tighten it up until it won't tighten no more, but I can pullthe stem and wheel in opposing directions and then notice the top cap has come loose. With the stem the 'right' way round it's fine.

Checked the stem and steerer and the only issues I could say is slight scratches to the paintwork (exposed silver under black paint) and some rusty and oily discolouration to the plain metal of the steerer. Both however feel smooth.

What on earth is going on here?
 

Banjo

Fuelled with Jelly Babies
Location
South Wales
Just tried it again, making sure I followed the instructions. Same problem.

It seems that turning the wheel with the stem inverted is unscrewing the top cap - I can tighten it up until it won't tighten no more, but I can pullthe stem and wheel in opposing directions and then notice the top cap has come loose. With the stem the 'right' way round it's fine.

Checked the stem and steerer and the only issues I could say is slight scratches to the paintwork (exposed silver under black paint) and some rusty and oily discolouration to the plain metal of the steerer. Both however feel smooth.

What on earth is going on here?

Dont know why you cant flip the stem but dont overtighten the top screw .It should be just tight enough to take any movement out of the headset.
 

g00se

Veteran
Location
Norwich
You could unscrew the top cap and it shouldn't matter as the the whole thing is being held in compression by the stem being clamped to the steerer - so the fact that the cap undoes and the the whole thing loosens, it must be that the stem cannot properly clamp the steerer when it's inverted.

Is anything fouling the stem/bars so it can't be tightened flat against the steerer? Try tightening the thing together away from the position you're tightening it currently - so if you're keeping the forks straight in line with the frame when doing this previously, try doing it with the forks and stem/bars pointing 90 degrees to the left. Also try removing/moving some of the spacers around in case one of these is damaged?
 
OP
Jezston

Jezston

Über Member
Location
London
Ok. Uh-oh.

I've just been trying the stem and spacers in various positions to see whats what. It was during these adjustments that I noticed something.

I don't need to unscrew the two screws clamping the stem to the steerer to take it off and move it around. The two screws are as tight as tight can be, and yet the stem moves freely around the steerer.

This isn't right, is it?

Also noticed after finishing my fingers had little silver particles on them. I have a horrible feeling that with all my playing around, I've knackered the thread in the screw holes in the stem. In a quick test, it wouldn't hold with the stem turned back again. Oh f*** ... ...
 

Howard

Senior Member
This isn't right, is it?
Er...no. This is why we have torque wrenches...

Also noticed after finishing my fingers had little silver particles on them. I have a horrible feeling that with all my playing around, I've knackered the thread in the screw holes in the stem. In a quick test, it wouldn't hold with the stem turned back again. Oh f*** ... ...
Unless it's a super light and pricey carbon or alu stem, in terms things you could break, they are pretty cheap to replace. Just buy a new one.
 
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