Self destructing Campy SR derailleur

Discuss light weight issues concerning road bikes & parts.
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by arthurf

Hi all,

Out riding this morning when my SR derailleur seemingly self destructed! It’s only 10 months old and has never taken any side impact but it seems to have failed just below the frame bolt. The hanger seems ok and I wasn’t cross chaining when it went. Any idea what could have caused this? Warranty claim?




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by kavitator


little stone gets in chain and jam ?

by Weenie

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by Calnago

From the looks of things.... the chain is jammed between the spokes and the largest sprocket and the position of the rear derailleur housing shows pretty clearly that the derailleur took a little journey up and around, versus just breaking off and settling where it is.... so, no warranty as it is due to the derailleur going into the spokes. But if a shop set things up not too long ago, and you really have no reason to believe the derailleur hanger had gotten bent in a fall or something, then I’d be taking it back to the shop since the lower limit screw was not adjusted properly. Unfortunately, your rear derailleur hanger did not break away during the process. Bad luck.
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by Butcher


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by wilwil

If the mech went into those spokes there would be damage or at least marks on the spokes.

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by bilwit

something made the chain get caught or stuck (dropped out of a jockey wheel and wasn't pushed back in maybe?) which pulled the arm as far as possible while pedaling until it was ripped clean off -- I had this happen to me in the past (luckily it was only a 105 RD)

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by Bridgeman

Years ago, I had this happen. I think it started when I felt a wheel from behind while on a large aggressive group ride. Maybe 15 minutes later my rear wheel locked up on a short downhill section. I might still have that mangled rear derailleur.

Turns out, the rear derailleur opened up into the rear wheel. I'm certain that rear-end I received was contact to the rear derailleur, thereby weakening the carbon fiber parallelogram.

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by kode54

this happened to me once on the older carbon SR RD. what happened to me was during the fall, when leaves are on the road and such. a little branch flicked up and got caught in my jockey wheels (i think), tore the hanger off and snapped the RD to bits. caused me to go down on a turn and caused damage to the rear wheel/spokes and chain stay. didn't break the chain stay (Storck bike at the time)...but gouged the carbon a bit.
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by arthurf

Thanks guys, looks like I’ll just have to suck up the cost for a new derailleur 👎

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by bm0p700f

If the chain is too short then that could be another cause of failure.

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by Bridgeman

Sometimes damage can take place without you being present. Coffee shops, where large groups frequent is an example.

I've experience damage from this type environment from a smug a**hole. I was lucky in that I was made aware of it as it was happening. Sometimes that doesn't happen.

Upon impact, components can be partially damaged, only to later fail when they have been cycled through their high stress excursions.

Sometimes it's kind of like catching a cold. You can never be absolutely sure where you picked it up.

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by Allen254

make sure hanger screws are tight and have lock tight

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by beeatnik ... stcount=23 ... stcount=40

Back in the Spring I built a Soma Fogcutter for an all-purpose bike. Campagnolo Chorus cranks with Potenza shifters and derailleurs, 11-32 cassette. I put several hundred road/gravel/single track miles on it without a problem or accident.
Yet on my first REAL gravel ride (in the mountains,think Southern Cross combined with Six Gap) the rear derailleur begins shifting poorly. I reach the lowest point on the route and the plastic knuckle on the Potenza rear derailleur separates/breaks, requiring me to single speed it (mostly uphill now) 40ish miles back to the car.
I noticed a lot of chain slap (on the descents) before the derailleur broke, and I expect this caused the knuckle to separate. I encountered no sticks and had no crashes on this bike up to this point.
I'm pleased with all of the Potenza components EXCEPT the rear derailleur. I've left that plastic part off of my bike from here on.

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by mattr

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