Cross chaining while backing up could lead to problems on top of the large cog, but shouldn't affect a situation that occurs between the bottom of the cog and the jockey wheel.
In my experience this problem almost always happened to users of bar end shifters. I assume it's too easy to bump the shifter and get the mech slightly off. Another issue is that about that time chains got slightly narrower and more flexible, so the inner plate should have been higher and closer to the jockey wheel.
At 6/30/2007 11:10 AM -0400, Tom Sanders wrote:
>I am wondering if the damage reported by some folks with derailleurs like
>Duopar might be from a bad habit that I just recently forced myself to kick.
>I often kick the bike down to a very low gear when about to dismount and
>park the bike or put it in the car or storage. The purpose, of course is to
>have the bike in an appropriate gear to set out with when getting back on
>the bike. In my case I usually neglected to change the front chainwheel
>before doing so and up with a severe cross chaining situation. Often the
>bike was balky when pushing it backward even with more modern derailleurs.
>Now I try and make an effort to get onto a smaller chainring before
>downshifting in the above situation and the bike never seems balky and I am
>still in a good gear to just hop on the bike and take off again. Not easy
>for me to do, as I am a slave to habit and once I get a bad habit, it often
>brings me a bit of grief.