Tim McNamara wrote:

Today there was a guy with a MTB and on the
chain stay there was a small drilled hole,
maybe 5mm in diameter. The hole didn't go
out on the other side so it was just one
entry point. It looked completely undramatic
to me but he said it reduced strength. Well,
of course, but not to a degree where the
tube would fail, right? I'd estimate the
tube diameter to 2cm plus change. It was an
old MTB, 90s or the Millenium, so does that
mean most likely steel and
possibly aluminium?

Metal bikes joined by welding, brazing, lugs,
etc., often have vent holes drilled into the
tubes near the heating site. The reason for
this is that the heat expands the air inside
the tube and the vent hole gives it
a controlled place to go- instead of, say,
sputtering out through the molten brass at
the joint. Usually this hole is about 1-2 mm,
but some are larger.

Thanks a lot, I CC this reply to him
right away

--
underground experts united
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