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I have a frame that I've built up and I'm having trouble getting the tension perfect on the headset, which is not usually something I have trouble with. A friend of mine who is much more knowledgeable than I about these things suggested that I should look into facing the head tube. I've read that it's not always necessary. Is there much truth to this?

edit: Nothing is damaged or chipped. The frame has its factory paint.

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Is it damaged, chipped? Has it been painted? –  cmannett85 Feb 7 '12 at 20:18
    
@cbamber85: I've updated. –  user973810 Feb 7 '12 at 20:59
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3 Answers

up vote 3 down vote accepted

In most headset designs, bearings sit between a pair of cups and races, one half on the fork steerer and the other half press-fit into the head tube.

If the cups are not parallel at both ends of the head tube, then you'll find it difficult to adjust the headset to the proper tension without binding - the cup will be meeting the race at an angle and it can seem too loose in some places and too tight in others.

The process of facing is ensuring that the ends of the head tube are parallel. The previous question of Why don't frame manufacturers ream/face their frames? addresses a little bit how a new frame can end up needing to be faced. In general many frames manufactured today don't need it, but if you are having issues it's certainly worth pursuing.

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Does it start out tight enough, but loosen as you ride it? I had an older steel frame years ago that would do this. The faces were not cut completely parallel so they had to be faced.

If it's been repainted as cbamber85 mentioned, it could also be affecting the seating of the cups.

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No, it is just seemingly impossible to get right to begin with. –  user973810 Feb 7 '12 at 22:07
    
Any chance it's out of round? If that's the case, I'm not sure facing it will help much b/c you're just be shaving off some metal to make the ends parallel, but still unable to accept the headset... What type of frame (AL or Steel) and what kind of headset are you using? I'm thinking of the old school types that have the cups pressed into the head tube. –  Don Feb 10 '12 at 18:40
    
It's almost certainly in round. It's a brand new frame. I'd be pretty surprised if it was damaged somehow. How does one check for roundness? –  user973810 Feb 11 '12 at 21:29
    
The frame I had the was having trouble was "mushroomed" out a bit b/c since the headset wouldn't stay tight, the cups were moving around and worked the metal out. With everything loose, I was able to push the cup in and out of the headtube easily w/out having to use any kind of a tool to set. Once the cup was in, you could wiggle it and feel play, so it was obvious there was no "grip" from the head tube. Hope that helps :-) –  Don Feb 13 '12 at 15:01
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For most modern, quality frames it is not necessary, unless you have a problem in which case it might be worth a try. Sometimes it's just a matter of getting down to bare metal, sometimes the tolerances are indeed a little off and the surfaces of the top and bottom of the headtube aren't perfectly parallel. There's less danger in facing a headtube than there is in facing a bottom bracket, as a headtube can be most any height- the same can't be said for bottom bracket shell width. You should read the answers to this question for related information.

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