That's a first for a failure
 

Finally took the Rodriguez out for a shakedown ride tonight. I had noticed the derailleur seemed to be a little loose in picking up chain slack in the small chain ring when putting the chain on. The bike ride great and absorbed road imperfections excellently. About 8 miles into the ride I looked down and saw the cage was vibrating a little. I was in the middle gear of the freewheel and riding easy. Figured I could make it home. About 30 ft later I hear a pop and then a spoke brake as the rear wheel locked.

Great! :thumb::(

Turns out it broke at the pivot where the A B position bolt is located. Needless to say I won't go back with a first gen Chorus derailleur. I should stay with Campagnolo. But I really like all my Suntour derailleurs. What would you do?

Photo for effect
https://cimg2.ibsrv.net/gimg/bikefor...f30b675db.jpeg

:eek:

Well after I finished crying, probably find an Athena D100.

:eek: YIKES!

Hate to say it but I think you got off easy, any more speed or torque and that goes far more wrong. ;)

Can't disagree with you there. Broke one spoke and bent another. The rest appear fine

^ Yep had an Ultegra RD body split and it caught into the spokes and clean through the seatstay on a new C.F. bike. One dead frame!

Bike is toast, I'll pay for you to ship it to me so I can take care of the issue. :D

The pivot bolt is the part that broke? I am trying to figure out from the photo/words and am still unsure what specific bit failed. I built up an Atala years back for the ex-wife and used one of these on that build. I wonder if it was a ticking timebomb...

Glad you didn't end up on the ground - or worse! Did the derailleur hanger suffer?

DD

Yikes. Glad it didn't turn out any worse. Last couple of times some friends had similar issues, one ended up on the deck (fortunately at slow speed), and the other had the entire rear derailleur and mount tear loose. If I'm recalling correctly the first was on a bike with electronic shifting and it overshot on the big cog and hit the spokes. Turned out the limit screw was fine but the RD cage had gotten bent somehow and hooked the wheel. In the other case the cyclist swore it was a manufacturing defect but, nah, she just cut the chain too short, then shifted into the big/big combo during a ride.

Pivot bolt is probably not correct phrasing - at least for most derailleurs. To tell you the truth I'm not sure exactly what broke. When I was on the road and frustrated I was thinking it looked to have broken at the extra screw by the B screw that was used to control the slant on the rear derailleur. But in the picture above that doesn't appear to be the case as that screw is visible next to the shifter cable and is not at the area that actually twisted and went into the wheel. Not to say that didn't fail and then caused the whole body to shift. I did take out that screw and look underneath and there is some sheared material. But, I don't know if that happened and caused the break or sheared because of stress because something else broke.

scozim will need to give a definitive answer, but it appears like the A-B adjustment actually saved the hanger! Who would've thought that feature would have come in handy?

Yikes! not good start, Scott. Glad it wasn't worse

Got a new, psychedelic avatar for you until you get this sorted. :thumb:

https://i.imgur.com/XM6S6S6.jpg

I'm using Victory with a 53/39 up front and 13-25 in the rear. The other bike that uses Victory is the usual 52/42 x 14/28. Both, 7-speed. If I use a 28t cog with the former, Victory has a problem with the chain slack. But it does the job quietly with both, given a clean chain.

I like Victory, 'cause it's good looking, light, easy to polish and won't break the bank. Don't tell anyone.

The more I look at the photo, the more I think the upper "pivot" screw loosened and allowed the body to shift. I am seeing a gap between the upper body and the parallelogram unit of about 1/8"; reviewing your photos from when you got the bike/cleaned it up, the transition is flush.

If you disassemble it and find the cause, please take pics and share here. I know there are bikes on the forum that use this very derailleur (I think Stuart has one on his DeRosa IIRC) and if it were me, I'd sure like to know what could cause a failure with such potential for catastrophe. Man, you got so lucky this happened at low speed - and gave you a warning first :)

DD

Derailleur hanger appears to be ok - just a little chipped paint in a couple of spots.

OK, that does it, I am scared off! I have the same RD that's almost installed on a Ciocc, but just stalled. I'm gonna retract that unit and find some other Campy RD. (whew!)

That A - B slant adjuster bold is quite stout, and surrounded by quite a bit of thick aluminum and bolts to a similarly stout part on the parallelogram. I'm wondering how it could even break. I have two bikes with first gen Chorus RDs on them and they have performed flawlessly (on non-indexed mode:rolleyes:). Was the A - B adjustment bolt tightened adequately??
wondering if this failure is just a fluke with this particular unit.

I feel your pain but mine involved a Suntour Cyclone M-II and a thumb sized stick.

https://cimg3.ibsrv.net/gimg/bikefor...0f6f5fe0b0.jpg

Glad you are ok and that it didn't take you down along with it! I vote for a first gen 8-speed or early 9-speed Ergo era RD. Classy, robust, and with the B-tension screw where it should be (mounted to a thick tab, unlike the 9s/10s stuff....). It should work quite well!

I did the same to a huret eco. Was able to bend it back. It even shifted between the 2 smallest cogs afterwards.

Agreed. The pivot bolt on the upper A-B adjustment became so loose that the four teeth that hold things in place no longer did their job.
It looks like the only broken thing on that derailleur is the cage.

I have a cage in good condition if you want to resurrect that derr. Alternately I would be interested in buying your derr. if the parallelogram pivots are nice and tight.
Brent

Thanks Brent. I took some photos this morning. As I told Drillium Dude last night about 1.5 miles before this I had noticed the chain seeming to have more bounce than normal in my shadow. I kept glancing at the rear derailleur and could see the cage vibrating side to side slightly which didn't make much sense. I suspect you are right in that the A B bolt somehow came loose. I had messed with it earlier in the day to see if it would help with the droopy chain issue I was having in the small chainring. I had tightened it back up but I suppose I could have messed something up and thought it was tight when it wasn't.


One of the teeth appears to be flatter/sheared/? In out if that group of 4 prongs to hold that portion of the derailleur. I don't know if that's what caused it to break or if it was a result of some other failed. All I remember is a pop sound and then the clang as the cage went into the spokes.

https://cimg4.ibsrv.net/gimg/bikefor...c4b84de0de.jpg

https://cimg8.ibsrv.net/gimg/bikefor...fc710e0d4b.jpg

https://cimg0.ibsrv.net/gimg/bikefor...517d2c180a.jpg

https://cimg4.ibsrv.net/gimg/bikefor...9073c5ed77.jpg

https://cimg6.ibsrv.net/gimg/bikefor...e99380bb63.jpg

https://cimg4.ibsrv.net/gimg/bikefor...358c8deab5.jpg

I think those locating teeth at the A-B joint were damaged from/after the cage getting twisted and might not the primary cause of failure... could be a jamb at the jockey wheels and chain that put a wrench in the works. Could it be inadequate tension from the lower pivot/Jockey wheel cage, combined with a stiff link on the chain?

Happy that was all the extent of the damage, but personally, I'd very carefully look at all the drive side spokes and probably consider replace/relacing all of them. I wouldn't want to think about a nicked spoke. I did see one spoke sheared off and another quite bent in your photo as you mentioned. Also, check the bent spoke to see if it started to pull out the hub hole.

Probably will never know exactly what happened. Chain was a brand new KMC.

Thanks for the photos.
Is it possible that when you tightened that A-B position screw, you did not get full true engagement between the teeth and the detents of the mating parts, so that you ended up with peaks against peaks? This would appear to be tight at first but only because the peaks have deformed each other as you see at 1 o’clock. Vibration would knock the pseudo joint loose and put slop in the interface. I know with mine I have to jiggle it a bit as I’m tightening the screws to make sure it is settling in, and have not tried to do that with the derailer mounted on the bike and chain running through it. (I just put it in A and left it there.). To my eyes this looks more like assembly error — maybe from a previous owner, even — than damage done to it from the mishap.
Things that are adjustable without really needing to be are usually a bad idea and likely this is why this innovation did not survive once Campag could use a true slant parallelogram design.

Glad you’re OK.