Does anyone know why the chain keeps on falling off on my Giant Seek 1, when I switch gears too quickly or when there is an extreme distance between the front and rear gears? I need to find a solution because it's making me crazy.

I went to my local bike shop and he said that there's nothing to adjust, and to just keep the front and rear gears lined up, somewhere in the middle at all times. What would be the purpose of having 27 speeds if I can't use them all? Thanks, John



2011 Giant Seek 1
1977 Peugeot PX10LE