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Old March 30th 05, 09:35 PM
David L. Johnson
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On Sun, 27 Mar 2005 21:16:11 -0600, Dan wrote:

Hi,

Because this is a hybrid I'm not sure whether to place it in racing or
off-road. But here goes my story.


*.racing trimmed off as irrelevant.

Saturday afternoon I was riding along a clean flat nature trail; no
sticks in the gears, no nothing. I was going at an even speed of
about 20-25mph in the next-highest gear when all of a sudden I hear a
*SNAP*, then something smashed into the rear spokes, causing an almost
instant stop. I was lucky I wasn't going downhill when this occurred,
or I would've flown over the handlebars.

It turns out that a small piece of the aluminum frame supporting the
gear shifter wore out due to metal fatigue.


How do you figure this was due to metal fatigue? I assume that this small
piece of aluminum is the derailleur hanger, which is not subject to a lot
of stress under normal use. In order to claim some sort of fault of the
manufacturer, you have to be able to convince them that this was the cause
of the problem. The rest of the damage was collateral.

In my experience, derailleurs usually snap off either because the chain
dropped and got tangled in the pulleys, which then twisted the derailleur
off since you were still applying pressure to the pedals, or there was a
missed shift under load, causing essentially the same chain of events. I
have seen both of these occur, one on the flat, and the other (the
missed-shift then crunch) on a short, steep climb. One other possibility
that can occur is if you shift it into the spokes, which is caused by a
misadjusted derailleur. However, I don't imagine this was the cause due
to the circumstances you describe.

Are you _sure_ you hadn't shifted at that point, or had the chain fall off
the chainring? I know it's easy for the dealer to just say it was
operator error and not take responsibility, but you need an explanation
why this was not the case here.


If the dealer or Trek will support the repair of this obvious
manufacturer's defect, I will keep you apprised.


Don't be surprised if the obviousness of the defect is missed by the
dealer. I don't see it, and would have to be convinced.

--

David L. Johnson

__o | A mathematician is a machine for turning coffee into theorems.
_`\(,_ | -- Paul Erdos
(_)/ (_) |


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