mkdevo

sooo... tried clipless for the first time on saturday. the first 20 minutes was hell, but things got *much* better after that.

anyways, during that first 20 minutes, i took a nice digger, during which, my chain popped off. i put it back on, but now it keeps falling off once i shift into a certain gear..

any easy way to fix this?

thanks in advance.

DMF 

Probably bent the rear dérailleur hanger. Shop time!

DannoXYZ 

WHICH gear are you in when it falls off? WHERE does it go when falls off? On the rear cogs or off the front-chainrings? Could be a big problem in the rear if it falls off the inside and chews up your spokes. Or it falls off the outside and gets the chain jammed between the cog and dropout. Falling off the front chainrings is different problem and the required fix is different.

mkdevo

- not sure what gear it falls off in. need to do some more testing.

- falls off in the front, not the rear.

intence

Is your bike new? Did the shop you bought it from mention anything about a tuneup? usually cables will stretch on a new bike. Check the following link on how to tune the derailleur if you can't take it to the LBS for some reason:
https://www.bikewebsite.com/ftder.htm

Adgooroo

OP - your front derailleur moves in and out to shift the chain from one chainring to the other. If it moves too far in either direction, your chain can/will fall off. The distance of the in-out move is controlled by small limiting screws on the derailleur mechanism. The screws are relatively easy to find and adjust - if you try to correct them, make small adjustments and note the effect as you dial in the setting.

As others have mentioned, the front derailleur may be bent or knocked out of alignment in a fall. It can probably shifted or gently bent back into alignment. Ideally, the cage that encloses the chain should be perfectly parallel with the line of the bike.

Also, shifter cables (and brake cables) stretch a bit on use, and need to be adjusted by taking up the slack. It isn't likely, though, that 20 miles of riding would cause the cables to stretch enough to drop the chain.

NOTE: If you are a new bike owner you should probably take your bike back to the LBS where you bought it and let them solve this problem for you. Almost all bike shops offer free adjustments during the break-in period.