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Old 12-12-07, 05:18 PM   #1
saibura
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Is this stem safe to use?

Hi all, I just wanted to get some opinions on this "new" stem I've bought. It was advertised as NOS, but has some mysterious markings on the underside, like so;





I contacted the seller, who said that it was perhaps just the finish on the stem. The the innerside of the clamp and the inserting column are clean as a whistle, no marks or scratches at all so odds are it is NOS after all. Has anyone ever seen markings like this on a stem, and am I going to die if I use it? Of course I won't hold anyone responsible, I'm just after opinions...
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Old 12-12-07, 05:39 PM   #2
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Looks like a casting mark. Depending on the depth, I would say it's completely superficial
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Old 12-12-07, 05:45 PM   #3
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+1 for casting marks, but you never can be too sure. Stems failing isn't too uncommon. What I would do is sand the underside down to make sure they don't go too deep. Maybe use a file or dremel (lightly). Then you'd want to polish it up.. here's a nice thread about how to do that: Do It Yourself (DIY)
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Old 12-13-07, 06:00 AM   #4
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thanks for the quick response - will give the ole file and polish a go!
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Old 12-13-07, 03:03 PM   #5
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Yeah, that looks to me like the mold wasn't up to temperature when that was cast, but I'd be pretty surprised if it was more than a millimeter deep.
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Old 12-13-07, 03:10 PM   #6
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+1 for casting marks, but you never can be too sure. Stems failing isn't too uncommon. What I would do is sand the underside down to make sure they don't go too deep. Maybe use a file or dremel (lightly). Then you'd want to polish it up.. here's a nice thread about how to do that: Do It Yourself (DIY)
Yeah, but the good news is they don't usually fail in that particular area.
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Old 12-13-07, 04:11 PM   #7
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Agree with the sand and polish.
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Old 12-14-07, 11:22 AM   #8
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I would think that emery tape that plumbers use would take those marks out and shine at the same time. If the marks did not come out I would be wary.
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Old 12-14-07, 07:46 PM   #9
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It looks to me like the stem is anodized, so sanding will ruin the finish unless you strip off all of the anodizing and polish the whole thing.

They look like scratches to me.
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Old 12-14-07, 08:28 PM   #10
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It looks to me like the stem is anodized, so sanding will ruin the finish unless you strip off all of the anodizing and polish the whole thing.

They look like scratches to me.
+1

It's on the underside of the stem. I personally would grease it up, put it on my bike, and ride it. I am not anal retentive enough to care about such things.
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Old 12-15-07, 06:04 PM   #11
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from experience with cars... anything NOS is just the assembly line rejects, id have to agree with poor casting on this but double check it just the same.
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Old 12-16-07, 07:29 AM   #12
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It looks to me like the stem is anodized, so sanding will ruin the finish unless you strip off all of the anodizing and polish the whole thing.

They look like scratches to me.
I agree. You will need to sand and polish the whole stem - and lose the finish - as if you sand + polish one area there will be a haze between the anodised metal and the sanded/polished. I suppose it will not matter if it is on a part of the stem which is not visible.

I would send it back to the seller, as it is not perfect at all - and I suppose in the back of your mind you may always be paranoid of it snapping...
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Old 12-16-07, 07:58 AM   #13
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Magnaflux it to be sure!
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Old 12-17-07, 05:21 PM   #14
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Magnaflux it to be sure!
Yeah, 'cause everone has that stuff lying around.
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Old 12-17-07, 06:05 PM   #15
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Magnaflux it to be sure!
So did you invent some new method to Magnaflux non ferrous metals?
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Old 12-17-07, 08:24 PM   #16
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I am pretty conservative regarding safety, so if it were my stem I would deep six it. Aluminum alloy is susceptible to fatigue breaking and some people recommend regularly replacing stems even when they show no signs of distress. Since your stem already shows irregularities, these are likely to become stress risers from which cracks may propigate at some point. Since no one knows what that point may be, why chance it ? I would be especially concerned if you regularly get out of the saddle to climb since you will be putting torsion in this area.

I'm not an expert and I've never seen a stem fail, so I'm not speaking form first hand experience - just what I've read. But my impression from what I've read is "don't mess around with stems"
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