I was on a ride a few months ago and while shifting, my chain came out of my derailleur. So this is a little confusing. Let me explain. The chain was resting on the outside of the bottom part of the rear derailleur cage. There is a little silver cylinder behind the lower jockey wheel that touches but doesn't actually connect the two sides of the cage. Somehow my chain go pushed to the outside of that. When it happened it felt like the chain had gotten shifted off and my cranks jammed up. I stopped pedaling as quick as I could.
Anyways, to get home I had to take out the bolt that secures the bottom jockey wheel in the cage, and open the cage up to get the chain back on the correct side of the silver cylinder. I put the jockey wheel back in with the chain in place and limped home.
I took the bike to the LBS and explained the problem. They didn't know what might have caused it. They checked the hanger, and it was a little out of alignment, but they said it wasn't that bad and fixed it. I also asked them to check that the derailleur itself wasn't bent, but who knows if they actually did that.
Flash forward to yesterday and the same thing happened. I fixed it the same way and limped home again. I've never seen this before and definitely don't want it to happen when I am sprinting.
A few things:
- My derailleur is an 11 speed Dura-Ace.
- Chain is not worn/bent/no frozen links
- Cassette is near new
- I was shifting both times, but not putting a lot of power down.
- Hanger should have been OK.
- The bike has less than 1,000 miles on it
- I didn't notice any wear on the bolt or threads and the bolt was tight as could be with locktite in the threads both times
Any idea what might be going on/how to fix it?