Headset tightens when I tighten stem bolts

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polar8
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Joined: Mon Nov 05, 2007 12:38 am

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

by Weenie


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TrekUk
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by TrekUk

Fork a carbon steerer?
Madone Five Series 2013
Shimano Dura-Ace 9000
Mavic Cosmic SLE 2013

polar8
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Joined: Mon Nov 05, 2007 12:38 am

by polar8

^Yes.

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TrekUk
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by TrekUk

over tightening causing it to squash putting pressure on the bearings most likely.
Madone Five Series 2013
Shimano Dura-Ace 9000
Mavic Cosmic SLE 2013

thisisatest
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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...

polar8
Posts: 52
Joined: Mon Nov 05, 2007 12:38 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.

FIJIGabe
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by FIJIGabe

How old is the stem? Is this a known issue, that may be warranty-able?
Madone 9 https://goo.gl/7UwZpV
Crockett https://goo.gl/f5PdCN
Madone 5 https://goo.gl/cMdyFo

Madone 4, Cobia. I own a lot of Treks.

thisisatest
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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.

by Weenie


eric
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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.

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