Originally Posted by
alcjphil
The front derailleur does more than shifting the chain from ring to ring, its secondary function is to keep the chain on the chainring. Modern chainrings are designed to facilitate shifting, so it is easy for the chain to fall off if there is no derailleur to keep it there.
Wouldn't this cause lots of complaints of FD chainrub? I guess I don't see this on my modern drivetrain. The chain only touches the FD when up or down shifting