Bicycle Mechanics - Simano 105 Rear Derailleur just snapped!
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01-31-07, 06:56 AM
I recently posted a thread about my Cannondale Cyclocross gear shifters not working:
I've had a more serious problem. I brought the bike to my local professional store for a complete service. However, today while cycling to work, the back derailleur and chain completely snapped. I carried the bike the rest of the journey to the same professional store. They were surprised saying they have never come across this problem with the Shimano 105 and said the problem is completely "abnormal" for this particular system. I have posted pictures here - http://picasaweb.google.com/mckay.joey/BrokenRearShimano
Where do I stand? I've written to the retailer in Boston and I'm awaiting their response. Should Cannondale replace all the damaged parts? Has anybody experienced the same problem?
Any assistance greatly appreciated,
Joey, it looks to me like the culprit in this domino effect is that popped chain link. Care to elaborate a bit about the terrain and gear combination you were riding in?
Coulda been worse without the 'dork disk' there. ;)
01-31-07, 07:34 AM
I have to assume the sequence of events was that the chain broke and the resulting loose chain distroyed the rear derailleur. One possible explanation is that the chain wasn't properly installed and it broke at the connector pin. Improper installation can causes this as 8,9 and 10-speed chains require the correct technique when installed.
Another possibility is that the bike picked up something from the road, a piece of wire, twig, etc., that got caught in the chain and caused the damage. I had a piece of steel wire get into my chain a few years ago and the results were similar to what you experienced.
01-31-07, 08:11 AM
Hi, I was cycling on a smooth tarmacamed main road. I was cycling in first gear. I was actually going to the Cycle Store as after the bike service on Monday, the gears were still slipping - for this reason I just stayed in 1st gear without changing gear at all. I can't understand how the chain would not have been installed incorrectly as it was brand new! The bike is literally just over a week old and I've probably cycled 5Km in total due to aforementioned problem with shifters and slipping gears. I doubt very much that a foreign object got stuck in the chain - I as examined the immediate area of road where the 'snapping' incident took place but I could be wrong. You are right about the 'dork disk'. It could have been worse - if there was damage to the wheel, I'd feel alot worse than I do now! The question still remains though - should I be able to claim for parts under warranty? Due the newness of the bike and the lack of useage and as advised by my local store, this problem with Shimano rarely occurs and even never witnessed previously by the bike mechanic in store...?
Take it up with the retailer. Only they can tell you if they are going to warranty it or not.
I was cycling in first gear.[/SIZE]
This doesn't give us much in the way of useful information - what do you mean by "first gear"? Were you in the small chainring in front and large cog in back? Or large in front, large in back? Or something else entirely? There's no consistent system by which bicycle gears can be referred to as "first," "fourth," "17th," etc. Describe which sprockets the chain were on - this is more meaningful information.
01-31-07, 05:56 PM
I can't see the chain pin clearly enough, but I bet the chain came loose at the join, so I would tend to blame the guy that put the chain on the bike. So if it is a new bike then go to who you got the bike from, if you had a shop install the chain go to the shop. If the shop you took it to did work that did not involve removing and reinstalling the chain then it is very unlikely that they had any thing to do with this.
A loaded shift can make a chain do this, but it still generally takes a poor pin install. The bike will usually give a warning before failing like yours, you can hear the chain link popping past the der before it comes far enough apart to catch like it did,
01-31-07, 07:52 PM
By first gear I meant, small chainring in front and largest cog in back. I'm starting to think Rev.Chuck (http://www.bikeforums.net/member.php?u=5461) is on the right track. I was bringing the bike back to the shop because the gears were slipping. Even in what I call '1st gear' there was a noise coming from the der (from what I can remember). Hindsight is always 20/20. I didnt know enough to prevent the breakage as the chain continued to rotate & I was almost at the shop. So now Ive to investigate if the shop made adjustments to the chain...and then who to point the finger of blame at! Is there a Bike Legal Issues forum yet or should I start one up. Only joking....still waiting for the retailer to return with comment but I can see me paying out of my own pocket for a new rear mechanism. Does anybody know where I can get a quality Shimano 105 rear mech for a good price - I'm pretty much out of pocket after paying $1400 for a bike a week ago that I still can't ride!!
01-31-07, 08:09 PM
I can't make out the failure mode of the RD in the pictures , but I had a similar incident when one of the jockey sprockets for the RD came loose. Bent the RD and broke the chain similar to yours. Tore off part of the jockey sprocket just the same too.
Your failure obviously wasn't the same as mine, The jockey sprockets are clearly fully attached to your RD in the pics. I'm just saying it's possible the RD failure could have started this, but I'm going with the others that an improperly installed chain is the most likely cause.
01-31-07, 09:18 PM
I have a rear 105 so this got my attention. I may be conflating incidents here, but I've gotten a twig stuck between the RD pulleys before that did damage to the chain. I then got what I thought was my indexing being off (you may have interpreted it as your gears slipping), but I kept riding, planning to work on the indexing that night. I never made it home with the chain intact, though. At one point, when I put an increased load on the drivetrain the chain broke. In retrospect, I think the twig damaged the chain and the "indexing being off" was actually a link with a loose sideplate running over the cassette.
The only way I can think of that would translate into a snapped RD, though, is if the link with the broken sideplate was stuck in the RD and the rider then put it under a big load.
01-31-07, 09:24 PM
You have just had the bike a week and bought it new? Did you take it to the shop you bought it from about the gear slipping? Then you should have less of an issue with getting this fixed. Generally the bike maker can be made to soak up the cost of the parts and the dealer will soak up the labor. If you bought it from one shop and had another work on it, then it is more unclear. The initial problem is that the person( a guy in Taiwan) that put the chain on goofed(But he installs 5000 a day and has a 99.9% success rate) It can be hard to tell that a chain is assembled incorrectly. The shop you took it to may have missed the problem, something they probably should have noticed, but still hard to lay on them(My dads heart doctor missed the cancer that killed him, but I still can't lay it on him even if I want to) Any way, you still need to do some talking to your bike maker and shop.
I've seen this happen on a new bike that had a tight link in the chain. When the tight link hit the rear derailleur it failed to go through, the derailleur twisted off the bike breaking the seat stay and damaging the chainstay ($300 factory frame repair). The owner had power washed the bike without re-lubing the chain.
02-01-07, 10:33 AM
I'd hope the shop could give some resolution with regard to the rear derailleur. If not shoot me a PM.
02-01-07, 09:29 PM
Thanks TO11MTM (http://www.bikeforums.net/member.php?u=50315), I will do. The retailer is currently in contact with Cannondale and I'm awaiting their call.
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