If you ever shift the front derailleur and experience the chain falling off the outside of the big chainring, don’t despair. You can shift the chain right back into place.
Many experienced riders aren’t even aware of this trick and would instead stop to put the chain back on by hand, wasting time and getting greasy.
The next time your chain goes over the big ring or falls off the small one and onto the frame, keep pedaling. Gently! Shift the front derailleur in the appropriate direction. The chain is very likely to catch the teeth and climb back on.
Don't force it and jam or bend something. If the chain won't catch, then you'll have to stop. Look for a twig or a piece of litter to lift the chain so you won't get too greasy.
This trick is no substitute for a properly adjusted front derailleur! If your chain is coming off as often as Phil Liggett says "live to fight another day," get your bike checked.
Another option for “chronic front derailleur syndrome” -- when no amount of adjusting seems to solve the problem of inside chain drops -- is a chain catcher.
You can buy these gizmos in many forms nowadays. They all work the same way, by forcibly blocking the chain if it goes beyond the small chain ring. You can also build one yourself cheaply and easily, using our own eArticle, How to Make a Chain Catcher.