Second broken derailleur hanger

This is a mystery failure, and I have no diagnosis.

For the second time in a year, my rear derailleur hanger has broken,
sending the derailleur into the spokes and locking up the back wheel.

I know that a common cause of this is shifting the derailleur into
the spokes, but -- and here's the weird part -- I wasn't shifting
the rear when it happened! I was on the third to the lowest cog,
when I down-shifted the FRONT into the small ring. Then things got
bad in a hurry.

I'm perplexed. I almost think that the hanger broke spontaneously,
which then sent the derailleur into the spokes. That's the only
theory I have at this point. Prior to the failure, I could hear a
rattling in the drive train when pedaling under force, but I
couldn't find the cause.

Bike is a 2004 Fuji Team SL, with a screw-on aluminum hanger
(thankfully). I'll post a photo of the broken hanger, if you think
it will help the diagnosis.

Thanks.
--
terry morse - Undiscovered Country Tours - http://udctours.com

Terry Morse wrote:
This is a mystery failure, and I have no diagnosis.

For the second time in a year, my rear derailleur hanger has broken,
sending the derailleur into the spokes and locking up the back wheel.

I know that a common cause of this is shifting the derailleur into
the spokes, but -- and here's the weird part -- I wasn't shifting
the rear when it happened! I was on the third to the lowest cog,
when I down-shifted the FRONT into the small ring. Then things got
bad in a hurry.

Keep in mind that a front shift into the small ring causes the rear
der's tension pulley to swing toward the rear quite a bit, and (grasping
at straws here) may cause some side-to-side swaying in the chain. That,
coupled with a momentary decrease in tension on the lower stretch of
chain (???)


I'm perplexed. I almost think that the hanger broke spontaneously,
which then sent the derailleur into the spokes. That's the only
theory I have at this point. Prior to the failure, I could hear a
rattling in the drive train when pedaling under force, but I
couldn't find the cause.

I too have had cause to regret not tracking down the cause of drive
train sounds. Sorry, no other clues to contribute, good luck.

Mark

Bike is a 2004 Fuji Team SL, with a screw-on aluminum hanger
(thankfully). I'll post a photo of the broken hanger, if you think
it will help the diagnosis.

Thanks.

Mark wrote:

I'm perplexed. I almost think that the hanger broke spontaneously,
which then sent the derailleur into the spokes. That's the only
theory I have at this point. Prior to the failure, I could hear a
rattling in the drive train when pedaling under force, but I
couldn't find the cause.

I too have had cause to regret not tracking down the cause of drive
train sounds. Sorry, no other clues to contribute, good luck.

Thanks, I have the hanger bits in hand. Looks like it bent, then
broke, as it's supposed to do. Oh well, at least I have a spare
hanger.
--
terry morse - Undiscovered Country Tours - http://udctours.com

In article ,
Terry Morse wrote:

This is a mystery failure, and I have no diagnosis.

For the second time in a year, my rear derailleur hanger has broken,
sending the derailleur into the spokes and locking up the back wheel.

I know that a common cause of this is shifting the derailleur into
the spokes, but -- and here's the weird part -- I wasn't shifting
the rear when it happened! I was on the third to the lowest cog,
when I down-shifted the FRONT into the small ring. Then things got
bad in a hurry.

I'm perplexed. I almost think that the hanger broke spontaneously,
which then sent the derailleur into the spokes. That's the only
theory I have at this point. Prior to the failure, I could hear a
rattling in the drive train when pedaling under force, but I
couldn't find the cause.

Bike is a 2004 Fuji Team SL, with a screw-on aluminum hanger
(thankfully). I'll post a photo of the broken hanger, if you think
it will help the diagnosis.

If you suspect hanger failure, examine both sides of the
fracture carefully under intense light. Is the fracture
all fresh metal? Or is some of the fracture corroded,
indicating progressive failure and the possibility that
the hanger fracture occurred first?

--
Michael Press

Terry Morse wrote:
This is a mystery failure, and I have no diagnosis.

For the second time in a year, my rear derailleur hanger has broken,
sending the derailleur into the spokes and locking up the back wheel.

I know that a common cause of this is shifting the derailleur into
the spokes, but -- and here's the weird part -- I wasn't shifting
the rear when it happened! I was on the third to the lowest cog,
when I down-shifted the FRONT into the small ring. Then things got
bad in a hurry.

I'm perplexed. I almost think that the hanger broke spontaneously,
which then sent the derailleur into the spokes. That's the only
theory I have at this point. Prior to the failure, I could hear a
rattling in the drive train when pedaling under force, but I
couldn't find the cause.

Bike is a 2004 Fuji Team SL, with a screw-on aluminum hanger
(thankfully).

Hold the thanks for a moment: how about the possibility that the screw
attachment came loose, causing the rattle, and then upon the shift
there was enough wobble to catch the derailleur in the spokes?

I think you have to proceed on the assumption that the derailleur
caught in the spokes and that that cause the hanger to break. The
question is, how did it catch in the spokes?

I'll post a photo of the broken hanger, if you think
it will help the diagnosis.

May as well. Do you have a long cage rear derailleur, or short?
t

On 2006-06-29, Terry Morse wrote:
For the second time in a year, my rear derailleur hanger has broken,
sending the derailleur into the spokes and locking up the back wheel.

I know that a common cause of this is shifting the derailleur into
the spokes, but -- and here's the weird part -- I wasn't shifting
the rear when it happened! I was on the third to the lowest cog,
when I down-shifted the FRONT into the small ring. Then things got
bad in a hurry.

This could be caused by the "chainsuck", chain not disengaging
from the larger chainring. Usually it pulls the RD just forward,
but with all the force of pedaling the RD might also get bent to
either direction.

More about chainsuck: www.fagan.co.za/Bikes/Csuck

Konstantin Shemyak.

Konstantin Shemyak wrote:

On 2006-06-29, Terry Morse wrote:
For the second time in a year, my rear derailleur hanger has broken,
sending the derailleur into the spokes and locking up the back wheel.

I know that a common cause of this is shifting the derailleur into
the spokes, but -- and here's the weird part -- I wasn't shifting
the rear when it happened! I was on the third to the lowest cog,
when I down-shifted the FRONT into the small ring. Then things got
bad in a hurry.

This could be caused by the "chainsuck", chain not disengaging
from the larger chainring. Usually it pulls the RD just forward,
but with all the force of pedaling the RD might also get bent to
either direction.

Thanks, I think chainsuck was the cause after all. I had another
chainsuck incident last weekend, but I stopped pedaling before
damaging anything. That's when I put 2 and 2 together. Chainsuck
pulls the bottom section of chain taut, and continued pedaling force
tears off the derailleur.

The clincher for this diagnosis is that I had just installed a new
chain: worn chainring + new chain = chainsuck.

The chainrings have about 16,000 miles on them, so I'm going to
replace both with haste.

And just in case someone is stuck with a broken derailleur hanger,
this web site is an excellent source for replacements:

http://derailleurhanger.com/

I ordered two, just in case.
--
terry morse - Undiscovered Country Tours - http://udctours.com