Originally Posted by
jppe
Normally the chain comes off the front....if that's the case it might mean checking the front derailleur. I assume the chain is coming off when shifting from the larger gear to the smaller one and dropping towards the frame?
The newer bike, the Trek (2010) was in the front and was more of a jam between the derailleur and the cage.
The Fuji had the chain come off the rear and needs the outer limit moved in a bit to prevent a reoccurrence.
Generally, though I think there is a problem when shifting in too extreme a movement. That is, say the rear smallest gear and shifting to the lower gear in front and vice versa. Think I have never had the problem when shifting the front gears when the rear chain is in the middle. Both bikes are two chain wheel bikes; the older one a 12 speed and the newer one an 18 speed.