Un-Chain my bike!

[sanuk]

In the process of changing my rear tire - a simple maneuver I've done a thousand times with little or no problems - my chain decided to slip off the front cog and get itself all in a nasty twist. The bike was on the floor upside down. At first I wasn't too worried, but then when I came to put the rear wheel back the chain got itself in a worse tangle that my efforts to straighten have only complicated. Now the chain is all in a terrible twist and jammed between the front cog and the chain guide and won't move - which of course is made worse by the tension of the derailer pulling backwards.

I guess I'll have to get a ride in someone's car to the nearest bike shop as otherwise I'll probably just make it worse. Just wondered what the experts might have to say. If this happened, as it quite easily could out in the middle of nowhere I'd be really screwed.

[Pat Lamb]

Prevention is relatively easy for this problem -- stop when the chain falls off and put it back on immediately.  (Do NOT keep pedaling if your chain drops while you're riding!)

There's usually a way to gently tug the chain out and fix the mess, and it's often coming at it from the other direction you've tried.  So if you've been pulling the chain from the top, try tugging it from the bottom.

If all else fails, you can partially disassemble the chain.  This may require a packet of replacement chain pins, which might push you to replace the entire chain ($10 vs. $25 for low end 9-speed pins and chain, for example).

Then make sure you've got a tub of GoJo or similar degreaser to clean your hands.  :/

[indyfabz]

If I am picturing what happened correctly, your chain doubled over itself, creating a loop. My GF did that a few weeks ago, and it's happened to me before.. If that's what happened, next time take a deep breath and work through the problem visually. With the chain on one of the chainrings, you know which is the side is the "underside" (the side that comes in contact with the sprockets of the chainrings and cogs, and which side is the "outerside" (the side that does not come into contact with the sprockets). Use that orientation to address the tangle.

[staehpj1]

If I am picturing what happened correctly, your chain doubled over itself, creating a loop. My GF did that a few weeks ago, and it's happened to me before.. If that's what happened, next time take a deep breath and work through the problem visually. With the chain on one of the chainrings, you know which is the side is the "underside" (the side that comes in contact with the sprockets of the chainrings and cogs, and which side is the "outerside" (the side that does not come into contact with the sprockets). Use that orientation to address the tangle.

I agree.  The language here seems a little confusing, but it sounds correct and I can't improve upon it.  I think that the key point is to think through where the chain is, where it is supposed to be, and in what orientation and you can always get it back into place,  Since it might require some force understanding where it is and where it wants to be is key.  You don't want to force it is a direction that it doesn't want to go.

The snag is usually where the chain crosses itself to make the loop that hangs it up.

In some cases it may help to unbolt the FD from the frame if the chain is binding in the cage, but I don't actually recall ever having to do that.

Bottom line...  Think it through first and then work it out.

[mbattisti]

did you look closely to see if the chain has a power-link that can be easily disconnected?

[sanuk]

Thanks for the words of wisdom. That's pretty much what I did. After a day of trying to forget it I finally went back to the basement and worked my way through. Amazingly, those nasty chain twists must have got the message and they almost un-did themselves for me.
Then it was just a matter of looping the chain back round the front cog. Lesson leant: If at first you don't succeed, try, try, try again.