Shifting Issues!!!!

It would have been helpful to know how your bike is configured, if it's a double or a triple crank. But generally speaking largest sprocket to largest chainring is a pointless combination to be in. You have the same gear ratio at other combos and it has the chain running at an extreme angle. It's called cross-chaining, and although usually doable it's generally frowned upon because of the above.
 
And why would you want to pedal backwards? Unless you need to tweak you position suddenly to avoid pedal strike, or maybe you're just getting bored/stiff during a long descent I have a hard time finding a reason for it. Don't expect any understanding from the bike mechanic if you complain about the chain not running clean while cross-chaining and pedalling backwards.
If it's a really new bike cross chaining might become easier when the chain gets a little bit worn and floppier sideways.
 
As for chain coming off on the inside: that's not supposed to happen, and another good reason for dork discs. Easy avoided with properly set end screws and a modest amount of shifting skills. Shiman shifters can often overshoot a bit if they get pushed to the very end of their stroke.

New cables stretch as they are used and need adjusted. This may or may not be an issue but one obvious thing to consider.

Thanks for the above comments that is very helpful. As far as the configuration it is a double crank and this is a brand new 10 speed bike. I was just worried I bent something. So it sounds like this is a normal occurance and not to worry about it as long as it is shifting correctly.

Quoted post said:

Originally Posted by dabac [IMG]/img/forum/go_quote.gif[/IMG]
Don't expect any understanding from the bike mechanic if you complain about the chain not running clean while cross-chaining and pedalling backwards.

LOL :-)
 
This is only funny b/c I am VERY picky when it comes to my bikes and I know I can drive my mechanics crazy sometimes. Not too long ago I asked our shop owner to adjust my shifting so that I wouldn't drop my chain when pedaling backwards while cross-chaining. He was nice about it (b/c he always is), but it was the first time EVER that he effectively told me that I had finally crossed the line and was now asking him for the impossible!!!
 
. . . his solution was for me to, "umm, just don't do that." and no, he could not understand why sometimes I need to pedal backwards (in silly gear combinations, nonetheless), and that was a tough one to explain :-)
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The situation you describe where the chain is drifting onto smaller cogs is NOT normal regardless of the direction the chain is moving ...
 
Since I cannot replicate the problem -- and, ignoring the fact that you probably have no reason to be back-pedaling when the chain is on the large chain ring and largest cog (which is really considered to be poor form because of the lateral stress you are placing on the chain regardless of the direction the chain is moving) -- I am going to suggest that ONE of the LINKS in your chain is binding ... that is, one of the PINs needs to be re-set so that the adjacent links move freely.
 
Another thing you may want to check is your rear derailleur hanger's alignment.

 
Quote: Originally Posted by alfeng [IMG]/img/forum/go_quote.gif[/IMG]

The situation you describe where the chain is drifting onto smaller cogs is NOT normal regardless of the direction the chain is moving ...
 
Since I cannot replicate the problem -- ... -- I am going to suggest that ONE of the LINKS in your chain is binding ... that is, one of the PINs needs to be re-set so that the adjacent links move freely.
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Came to think of another possibility: Changing gears while coming to a stop can cause the chain to wander if one were to pedal backwards at that moment. Happens to me sometimes when I failt to time an intersection/light correctly and have fumble around to get the pedals in a good starting position. But that's stretching the definition of pedalling a bit.

To clarify I am not actuually on the bike. I noticed this after I adjusted the rear derailluer while my bike was in a stand. I was going through all the gears trying to make sure everything was adjusted corecctly. It seems to shift great up and down the cassette. I also checked the chain and all of the links move freely. The rear derailluer appears to be straight but I did not put an alignment tool on it.