Most of the time, a skipping chain is caused by cable stretch. In the first half dozen rides on a new bike your shift cables stretch the most. They can also stretch over time as you ride. Hippley explains, “It takes cable tension to open a derailleur, which shifts your chain between gears.

When I pedal backwards my chain comes off?

Adjusting your rear derailleur limit screws

If your chain is coming off at the rear, it's often a simple matter of adjusting the limit screws on your rear derailleur. ... If your chain is coming off the outside of the cassette, put the chain onto the larger chainring and the smallest rear sprocket.

Why does my bike chain slip when I pedal hard single speed?

Anyway, when you're pedaling hard, there is tension in the top section of the chain, between the ring teeth and the cog. Under this tension, they stay engaged even if the returning-to-ring section of the chain is sagging.