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Headset tightens when I tighten stem bolts

Posted: Tue Apr 30, 2013 8:48 pm
by polar8
I have a weird phenomenon happening with my CAAD10 build. I've built hundreds of bikes before and have never experienced this.

When I'm installing the stem, I tighten the top cap to a reasonable level where there is no play but the headset still turns smoothly. At this point I would just align the stem with the front wheel, tighten the stem's pinch bolts, and call it a day. But when I go to tighten the pinch bolts, the headset gets progressively and significantly tighter (harder to turn). It's actually preventing me from riding the bike because I can't properly adjust the headset. Either there's play, or I can't turn the bars.

Anyone have any idea what's going on here? Oh, and I'm using a Pro Stealth Evo integrated handlebar.

Thanks

Re: Headset tightens when I tighten stem bolts

Posted: Tue Apr 30, 2013 9:12 pm
by TrekUk
Fork a carbon steerer?

Re: Headset tightens when I tighten stem bolts

Posted: Tue Apr 30, 2013 9:12 pm
by Weenie

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Re: Headset tightens when I tighten stem bolts

Posted: Tue Apr 30, 2013 9:22 pm
by polar8
^Yes.

Re: Headset tightens when I tighten stem bolts

Posted: Tue Apr 30, 2013 9:25 pm
by TrekUk
over tightening causing it to squash putting pressure on the bearings most likely.

Re: Headset tightens when I tighten stem bolts

Posted: Wed May 01, 2013 2:07 am
by thisisatest
My guess is that the bottom of the stem is not square with the headset top cone. When it's loose, everything is fine. but when you tighten the stem, the "crooked" stem bottom forces the top cone crooked as well, causing it to drag on the frame.
Top cone=upper bearing shield, top bearing cover, etc...

Re: Headset tightens when I tighten stem bolts

Posted: Wed May 01, 2013 6:41 am
by polar8
^You got it. Turns out the bottom back side of the Pro Stealth Evo stem is simply not flat. The front side has a 1mm gap when looking at it from the side. So when I tighten down the top cap, it forces it flat. But then when I tighten the pinch bolts, it wants to go back to its normal position (which is to say, a crooked bottom).

Any suggestions? I'm considering taking a file to the part of the stem that's sticking out.

Re: Headset tightens when I tighten stem bolts

Posted: Wed May 01, 2013 8:30 pm
by FIJIGabe
How old is the stem? Is this a known issue, that may be warranty-able?

Re: Headset tightens when I tighten stem bolts

Posted: Thu May 02, 2013 3:07 am
by thisisatest
Yay, me!
You can file it if you want. if it's under warranty, do that instead, of course. It is possible, although unlikely, that some bike shop has a Stein stem facing tool. I think Chris King's facing tool can be configured for stems as well.
The occasional stem has this issue. most of the time, it doesn't even affect anything.

Re: Headset tightens when I tighten stem bolts

Posted: Thu May 02, 2013 3:52 pm
by eric
You could clamp the stem to an old chunk of steerer tube and then face the stem with a lathe or milling machine. Or by hand with a file if you have a steady hand.

Re: Headset tightens when I tighten stem bolts

Posted: Thu May 02, 2013 3:52 pm
by Weenie

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