Front Derailleur- 2 or 3 chainrings
I just bought a used bike and am adjusting the front derailleur, and am wondering if its possible that my 2 chainring bike has a 3 chainring derailleur. Or are all derailleurs alike, and I just need to bring in my limits? How can you tell?
You should be able to set the limit screws to make the DER work, IF that was your scenario. A DER has to have some adjustability to handle slightly different spindle lengths/cranks.
Set the LOW limit screw to keep the chain from falling off the small ring. Then, with the DER on the small ring, pull the slack out of the cable. Adjust H screw so chain doesn't fall off the other side of the big ring.