[tober1]

On my commuter bike I can't seem to make the handlebar sit snug in the stem. It keeps rotating toward the front as soon as I hit a bump.
It's a 1" quill stem and appropriate bar. Only 1 bolt on the stem, just beneath the bars.
Seems I should be able to get something between the two that would allow for a little more 'grip'. So far I've tried a strip from a soda can, but no luck.

Is there a point when the stem/bars just won't 'catch'?

Any advice is appreciated.

 

[Kerry Irons]

Bar size

On my commuter bike I can't seem to make the handlebar sit snug in the stem. It keeps rotating toward the front as soon as I hit a bump.
It's a 1" quill stem and appropriate bar. Only 1 bolt on the stem, just beneath the bars.
Seems I should be able to get something between the two that would allow for a little more 'grip'. So far I've tried a strip from a soda can, but no luck.

Is there a point when the stem/bars just won't 'catch'?

Any advice is appreciated.

You say that it is the right size bar, but then say you put in a shim. Typically there would not be enough room for a shim if you had the right sized bar. That said, one standard fix would be some hair spray. Another would be some carbon fiber assembly paste - essentially grease with some grit in it. If the bars and stem truly do match, this should not be a problem.

 

[SilverStar]

If it's an old quill stem and bar, it's possible that the bar diameter is 25.4mm (many old drop bars had that diameter) and really doesn't fit the stem. Kerry's right -- if it WAS right, no shim could fit in there.

Add another shim if you can or try some of his other suggestions.

 

[tober1]

It's the right size handlebar 25.4 and the right size stem. I just can't seem to get it tight enough. And the shim is literally the width of a piece of aluminum from a pop can, not wide at all. I had to pry it open to fit it in. It held better than before, but still slipped.
I'll try some hair spray or carbon paste.
I'm wondering if the bar is just too old and the striations are worn down that typically hold it in place..

 

[Kuma601]

What stem and what bar?
What is the measured diameter of the bar?

I suspect you have a 26 clamp stem with a 25.4 bar. Though the soda can should get you close if this is the scenario.

 

[cyclust]

another option is to use a very light coat of spray contact cement of the bar. Just mist on a very light coating [mask off and only apply where the stem makes contact]. Let it dry for at least 24 hours beofre re-installing stem. This will add quite a bit of tackiness to the bar. It worked for me on a seatpost that kept slipping!

 

[brblue]

to add my 2c you can combine/replace the coke shim with a sandpaper one. (fold the paper so it's gritty on both sides) Agree though that you should get a stem with a smaller clamp, or simply a different make of stem with the same size clamp. (if it were a 26.0 stem with a 25.4 handlebar, the stem clamp ends would join before the bars are fixed to a satisfactory degree. is this your case? )

 

[SilverStar]

It's the right size handlebar 25.4 and the right size stem. I just can't seem to get it tight enough. And the shim is literally the width of a piece of aluminum from a pop can, not wide at all. I had to pry it open to fit it in. It held better than before, but still slipped.
I'll try some hair spray or carbon paste.
I'm wondering if the bar is just too old and the striations are worn down that typically hold it in place..

That's definitely possible...or the clamp on the quill is just worn out from overtightening in the past (prying it open to put in the shim may not have helped that ).

I like the sandpaper-shim idea...some things to try here before you spring for another bar/stem!

 

[jmlapoint]

How about a coating of Hair Spray?
Goes on liquid, allows time to adjust and tighten, and then drys to hold bar/stem.

john

 

[tober1]

Sandpaper idea. Brilliant. Worked like a charm.....so far
They are definitely the right size. Both measured with calipers. I'm assuming one has been overtightened too much and the other has been clamped to often. Both were used items so I'm not totally surprised.

Thanks for the ideas everyone.

 

[foofighter]

bump, i'm trying out figure out what they use to spray handlebars in the area where the stem clamps and brifters are clamped on.

anyone?

 

[Kontact]

bump, i'm trying out figure out what they use to spray handlebars in the area where the stem clamps and brifters are clamped on.

anyone?

Who's they and what spray? Most silver bars are bare aluminum, and black bars are either anodized or powdercoated. There is no traction product sold for clamping aluminum parts together. For carbon, there is carbon paste - which is not a spray.



OP-

What brand and model of stem do you have?

If the two contact areas are slipping because they've become too smooth, rough them up with 60 grit sand paper perpendicular to the slipping.

But I suspect a mismatch and/or a clamp bolt issue. I have never seen a correct sized stem that didn't nearly crush the bar.

 

[FBinNY]

If it continues to slip, visit an auto engine rebuilder and see if you can swap a beer for a dab of coarse lapping compound.

This is basically grit in a grease base. When applied between two surfaces under pressure the grit bites into both providing a mechanical interlock. It's analogous to putting sand on ice for traction.

Apply the lapping compound to the clamped area, position the bar then clamp. Important do not try to reposition the bar with the clamp only slightly loosened, the grit will cut will cause circular scores in the bar and defeat the purpose, so be sure to loosen completely before moving the bars.

 

[foofighter]

my bad should have been more clear. it's a textured finish that's sprayed onto mainly carbon bars. you'll have nice smooth clear coat finish until you get to the stem and brifter area and it's got a rough coating of something on it.