Originally Posted by
rydabent
The fact remains that if you turn your pedals backward, or roll the bike backwards and gears change, something is misadjusted. Either the hanger is bent, or the RD is not adjusted right.
No, absolutely not, most definitely not, no.
When turning the drivetrain backward, the chain is going from the cassette to whatever is below -- RD & hanger -- so they cannot affect how the chain is feeding onto the cassette at the top. It's totally obvious if you think about it for even 2 seconds.
OTOH
if the OP was reporting a problem with the chain coming off the bottom of the chainrings when back pedaling, then the hanger or RD might be implicated since they determine where the chain would be coming from as it moves to the bottom of the ring.