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Old April 13th 19, 02:29 PM posted to rec.bicycles.tech
AMuzi
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Posts: 13,447
Default A hole in the stem

On 4/12/2019 10:15 PM, Joy Beeson wrote:


I don't recall whether my handlebars came with the Raleigh Carleton or
the Fugi Grand Tourer -- we swapped components rather suddenly when a
mechanic overhauling the Raleigh found a defect in the brake bridge
that was above his pay grade. I don't think I ever knew whether the
handlebars and stems were included in the swap; we just left both
bikes with the mechanic.

It says "GB" in a circle in a recessed diamond on the stem.

Just above the point of the diamond, an adjusting barrel for the front
brake cable is set in the top of a hole through the stem.

I read somewhere that drilling a hole through the stem is a terrible,
horrible idea, and it makes sense that one should avoid weakening such
a vital component, but it's a tempting idea: It looks neater, it
makes the path of the cable slightly smoother, and it makes the cable
a more convenient place to hang my gloves.

So as long as the hole is there I might as well use it, but the
mechanic at the Trailhouse routes the cable around the stem, as if
there were no hole.

I'm going to have the bike overhauled pretty soon, and I'm thinking of
telling him to use the hole -- but is there some *other* reason why
routing a brale cable through the stem is a bad idea?


Yes it's a point of stress concentration on a part not
overly strong and, in the classic era of cast aluminum, your
stem may well have voids or inclusions you can't see.

That said, there's plenty of 'prior art':
http://www.yellowjersey.org/photosfromthepast/am19f.jpg

I've seen plenty of failed cast aluminum stems, old and new:
http://pardo.net/bike/pic/fail-001/FAIL-057.html

which is not to say welded stems are immune:
http://pardo.net/bike/pic/fail-001/FAIL-101.html

but haven't seen an actual failure from a hole drilled in a
stem.

So, yes, it's a bad idea in principle but may be OK in
practice. Given its age (aluminum does age-harden) and the
low cost of a forged or thixoform stem, change it if that
bothers you.
--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971


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