Originally Posted by
filtersweep
I hope you are joking. On a road bike, the derailleur rather gently takes up the tension of the chain--- allowing it to shift easily. They also have ramps to promote shifting, and the teeth are not cut uniformly for a reason.
I'm joking about it being harmless, but I do it sometimes when I don't have a wrench on me and there is no other option. It's always done with teeth gritted and prayers to Mardok that I don't break a tooth.