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Main
Date: 11 Nov 2007 08:26:42
From: crash
Subject: chain jumps off of the middle chainring
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Ive been having this problem for months now. Ive got a Giant boulder
se and the chain jumps completely off of the middle chainring not even
onto the bottom ring. Ive had the bike for 4 years and has NEVER
slipped once. I broke the rear axle earlier this year and had my lbs
replace the rear wheel and cassette. I rode the bike maybe 6-8 times
and then the chain started slipping in the middle chainring. Took it
back to lbs and they said the rings were bent and needed to replace
them. They also replaced the bottom bracket and the chain. So the
whole drivetrain is brand new. It kept jumping off the middle ring so
I took it back 3 times for the same problem and the 3rd time they
replaced the chainrings with a new set. I rode the bike and it did
better but still slipped and when I got done riding I noticed that the
subframe was cracked almost in half. Went back to lbs and they
replaced the frame. We all figured that this would fix the problem
but it didnt. So I went to another bike shop for a second opinion.
They couldnt get it to jump off either and said that everything was
adjusted perfectly. Im sure they all think Im crazy but the chain
still jumps off ONLY in the middle chainring. I can ride anything in
the high or low gear and it wont slip or jump or anything. So after
having everything replaced 2 bike shops and 8 mechanics later it still
jumps off and everyone says everything is perfect. It jumps off when
Im in the middle gear and hit a root or torquing up a hill and hit a
bump or root. It really sucks to be cranking up a hill and the chain
jump off and you flip over the front of the bike. If anyone can
possibly give me a little help it would be very appreciated.
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Date: 12 Nov 2007 10:33:32
From: Peter Cole
Subject: Re: chain jumps off of the middle chainring
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crash wrote:
> Ive been having this problem for months now. Ive got a Giant boulder
> se and the chain jumps completely off of the middle chainring not even
> onto the bottom ring. Ive had the bike for 4 years and has NEVER
> slipped once. I broke the rear axle earlier this year and had my lbs
> replace the rear wheel and cassette. I rode the bike maybe 6-8 times
> and then the chain started slipping in the middle chainring. Took it
> back to lbs and they said the rings were bent and needed to replace
> them. They also replaced the bottom bracket and the chain. So the
> whole drivetrain is brand new. It kept jumping off the middle ring so
> I took it back 3 times for the same problem and the 3rd time they
> replaced the chainrings with a new set. I rode the bike and it did
> better but still slipped and when I got done riding I noticed that the
> subframe was cracked almost in half. Went back to lbs and they
> replaced the frame. We all figured that this would fix the problem
> but it didnt. So I went to another bike shop for a second opinion.
> They couldnt get it to jump off either and said that everything was
> adjusted perfectly. Im sure they all think Im crazy but the chain
> still jumps off ONLY in the middle chainring. I can ride anything in
> the high or low gear and it wont slip or jump or anything. So after
> having everything replaced 2 bike shops and 8 mechanics later it still
> jumps off and everyone says everything is perfect. It jumps off when
> Im in the middle gear and hit a root or torquing up a hill and hit a
> bump or root. It really sucks to be cranking up a hill and the chain
> jump off and you flip over the front of the bike. If anyone can
> possibly give me a little help it would be very appreciated.
>
I'd make sure that there is no drag in the freewheel mechanism. Drag
there can cause the upper chain run to slack when you coast, add a bump,
and you'll toss a chain. Since this problem started soon after rear
wheel & cassette change, the cassette may be dragging slightly (often on
spoke protector). Also check the chain line. Another (long shot) is
that, since the rear hub was changed, the freehub pawls might be
slipping under high torque, that could throw enough slack to toss the
chain (should also happen in granny too though).
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Date: 11 Nov 2007 11:20:05
From: Tom Sherman
Subject: Re: chain jumps off of the middle chainring
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"crash" wrote:
> ...It really sucks to be cranking up a hill and the chain
> jump off and you flip over the front of the bike....
With a user name like "crash", what do you expect? ;)
--
Tom Sherman - Holstein-Friesland Bovinia
Tradition is the worst rational for action.
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Date: 11 Nov 2007 20:45:34
From: jim beam
Subject: Re: chain jumps off of the middle chainring
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Tom Sherman wrote:
> "crash" wrote:
>> ...It really sucks to be cranking up a hill and the chain
>> jump off and you flip over the front of the bike....
>
> With a user name like "crash", what do you expect? ;)
>
in your sig:
"Tom Sherman - Holstein-Friesland Bovinia
Tradition is the worst rational for action."
that should be "rationale", not "rational".
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