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Odd chainstay damage

Old 07-30-20, 10:32 AM
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dabac
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Odd chainstay damage

Hi all,
I brought out what was intended to be the next flip bike, and discovered a strange chainstay damage:

Weird chainstay crack
Any ideas of what caused this?
There’s no lateral impact to the bike. The edges are reasonably thick, so not rusted out. The sides of the crack are significantly displaced, so it’s not fatigue.
Water gotten into the stay, frozen and blown it apart?
Has there been a bracket welded on there (Maybe a chaincase mount) that someone has torn off? Weird place for one.
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Old 07-30-20, 10:39 AM
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onsay99
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Looks like frost heave from the posted pic. This is caused by
water freezing inside the tubes of an outdoor stored bike and
busting the tubing from inside out. Not easily repairable.
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Old 07-30-20, 12:31 PM
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Looks like a junk bike to me. Not uncommon to get scratches there from dropped chains. Water gets on the paint and rusts through. No big mystery.
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Old 07-30-20, 01:41 PM
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Originally Posted by Pop N Wood
Looks like a junk bike to me.
Well, it might be junk NOW.
Otherwise it’s a Ridgeback:https://www.ridgeback.co.uk/
While no De Rosa or Surly, it seems to have started life as a decent enough bike.

Originally Posted by Pop N Wood
Not uncommon to get scratches there from dropped chains. Water gets on the paint and rusts through. No big mystery.
... except that there’s good thickness at the exposed edges. None of that thinning out that I’d expect from a rust-driven failure. Nor would rust explain the displacement of the edges from each other and from the shape of the stay.
Originally Posted by Pop N Wood
Looks like a junk bike to me. Not uncommon to get scratches there from dropped chains. Water gets on the paint and rusts through. No big mystery.
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Old 07-30-20, 03:00 PM
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Well then go ahead and put money into fixing it up.

Once the top rusts through all bets on structural integrity are off. Might have even rusted from the inside out.
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Old 07-30-20, 03:39 PM
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The only thing that would cause a bulge type failure like that is water pooling in the stay and freezing. The bike appears to have been left outside and water probably entered through the seat tube and filled the bottom bracket and chainstay. A bottom bracket drain hole could have prevented that.
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Old 07-30-20, 05:32 PM
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Salvage some parts, then flip the frame ........... into the local dump.

"... intended to be the next flip bike,...
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