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Framebuilders Thinking about a custom frame? Lugged vs Fillet Brazed. Different Frame materials? Newvex or Pacenti Lugs? why get a custom Road, Mountain, or Track Frame? Got a question about framebuilding? Lets discuss framebuilding at it's finest.

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Old 04-04-13, 06:43 PM   #1
mainstreetexile
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Steel+aluminum quill stem - reliability concerns?

First, I'm not sure if this is the best place to ask this, so feel free to send me on my way. But I figured you folks may have a knowledge of the materials and fabrication methods involved.

I have a quill stem on one of my bikes that is very tall and very short. I know that it looks strange, but I bought it on a whim to convert a vintage mtb frame (with a very long top tube) to use as a drop-bar all-rounder style bike.

The stem apparently uses steel for the tall insertable quill portion, with a forged aluminum head.

I'm not exactly sure how these two parts are mated, but I'm curious about the longevity of this and how it will hold up over the long term. Can anyone weigh in on how this was made and if I should be worried that the two parts may eventually break free?

I've been considering getting a custom steel LD-style stem made to approximate the dimensions of this stem, but if this will hold up for the long-term, I don't mind using it.

Here's a picture of the stem in question:

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Old 04-04-13, 07:01 PM   #2
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No matter how it was made, if the top of that bolt bears on the aluminium portion (and presumably the bottom cinches the bottom of stem inside the steerer) then as long as the bolt is done up the two parts can't separate so there's nothing about which to worry.
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Old 04-04-13, 07:03 PM   #3
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I'd be more concerned with the quill bending then the extension coming loose. What kind of riding/use are you planning? Just tooling around or getting big air? Andy.
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Old 04-04-13, 07:57 PM   #4
mainstreetexile
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Thanks for the replies so far.

Quote:
Originally Posted by Andrew R Stewart View Post
I'd be more concerned with the quill bending then the extension coming loose. What kind of riding/use are you planning? Just tooling around or getting big air? Andy.
No big air, jumps, serious mountain biking, or anything like that. I use this bike for most of my riding lately: everywhere around town, some longer rides, some short touring, and some dirt road/light trail riding. Possibly a slightly longer baja or pacific coast tour later over the next year or so.
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Old 04-05-13, 10:09 AM   #5
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If I had to guess, it's a press fit. Done right it should be very strong.
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Old 04-05-13, 06:01 PM   #6
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Shrink fit? A straight press fit seems too likely to potentially be torqued out of alignment.
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Old 04-05-13, 06:21 PM   #7
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I think they were swaged together. Aluminum cranks are sometimes swaged to the rings so that the same castings/forgings can be used for the left and right arms, this is typical of vintage entry-level stuff but this stem isn't subject to the same forces and as Mark Kelly mentioned the whole thing is secured by the bolt so it's nothing to worry about as long as the stem is inserted past the line.
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