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Uneven stem facing. Problem with headset tension?

2129 Views 5 Replies 5 Participants Last post by 4JawChuck, Jan 6, 2010

yokine

Discussion Starter · Jan 4, 2010

I borrowed a head stem to try out a different riding position. After install I noticed that the spacers were "kicking up" at the front and there were paper thin gaps between them and the headset. It appeared that the stem was not faced parallel top and bottom. What worried me was that the headset was being tensioned un-equally, more at the back, causing uneven wear or binding of the bearings. See picture for clarity and measurements using a calliper.

Am I worrying about nothing or should the stem be junked?

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reptilezs

· #2 · Jan 4, 2010

could also be uneven spacers

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beeglemania

· #3 · Jan 5, 2010

If you actually measured those dimensions with a caliper I'd scrap the stem, that's a big difference. Are you sure the head set is seated properly and the head tube has been faced? These seem more likely to be the problem.

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yokine

Discussion Starter · #4 · Jan 5, 2010

The stem was measured with a vernier caliper. Other stems I have had on there looked "right" and this one looked "odd", and the measurements confirmed the visual. I'm pretty certain the stem is junk, but wanted to check peoples opinions on whether it could do damage to the headset, rather than just looking rubbish.

But yeah I agree that it always makes you think about how well the head tube is faced or the cups installed.

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steiny

· #5 · Jan 6, 2010

yokine said:
The stem was measured with a vernier caliper. Other stems I have had on there looked "right" and this one looked "odd", and the measurements confirmed the visual. I'm pretty certain the stem is junk, but wanted to check peoples opinions on whether it could do damage to the headset, rather than just looking rubbish.

But yeah I agree that it always makes you think about how well the head tube is faced or the cups installed.

I've been through this on several stems (Thomson, Easton, Race Face). Some worse than others, but none were flat according to my micrometer. Depending on what headset you are running, it can make a big difference. Chris King headsets, with their retarded O-ring setup, will creak and loosen on any stem not flat within 0.001". I only run headsets with compression rings now primarily because of that - they are much more forgiving for stems that are not exactly flat on the bottom and perpendicular to the bore.

If the bottom edge was not machined flat - lots of forged stems aren't - then they can be off quite a bit. I measured one that was almost out by 0.01" from front to back. Totally ridiculous.

If your headset is not creaking, it's staying tight, and it's not binding when you turn it, I wouldn't worry too much about it.

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4JawChuck

· #6 · Jan 6, 2010

Take it back or file it flat, I had one like that too. Cheapo Bontrager from the parts bin for the wifes bike. I would have taken it back but it was free so I filed it flat...might have to do both sides since it seems the taper is on both side of these cheap stems. Yours is only out 0.028", might take 15 minutes to get it square.

Mine works fine now.

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