Why does my bike chain fall off when I pedal backwards?
If it has a derailleur your gears need adjusting. We properly adjusted shifting system will allow you to pedal backwards without the chain coming off. Something could be bent, like the derailleur hanger or the derailleur itself. If it’s a singlespeed, this means the chain is out of alignment with the two sprockets.
Why is my chain falling off?
It might be that the chain is worn, has a stiff or bent link, or has become clogged up with dirt. A visual inspection while turning the cranks should reveal if there’s a problem here. The chainring, or a chainring tooth, could be bent. Again, a visual check will tell you what you need to know.
What do the screws do on a rear derailleur?
Derailleurs are fitted with limit screws that stop the derailleur from moving too far inward or too far outward. If you look closely as the derailleur moves, you can see the limit screws stopping the derailleur at each end of it’s travel.