Campy '15 Front Derailleur Behaviour
 

My Chorus '15 front derailleur has about 1500 miles on it, and, noticing that it was occasionally throwing the chain off when shifting to the big ring, I adjusted the limit screws. I adjusted it enough that I needed help from the LBS to get the cabe tension correct again. I was surprised after their adjustment that, when shifting from big to small, the ergo shifter only allowed two clicks at once, which was *just* enough to get it off the big ring. Before the adjustment and since I had the bike built, I was able to push three clicks down in a single shot. LBS guy said that the two clicks was expected so that you don't over throw the chain, and I can still shift one more time after the two to trim. Is this expected? My last bike had 90s-era Ergopower shifters so I have no recent frame of reference.

Thank you!

My first test on a FD not acting right is to shift to the larger ring then relax. I then pull the cable from the frame and see if it still has a tiny bit of travel before it hits the limit stop.

If it's correctly set up (by my standards) there should be a bit of over-travel that this will detect.

Unfortunately too many people use the upper limit stop, who's sole purpose is to prevent overshifting and dumping the chain, as a trim adjustment. To properly set up the FD, back the limit off and out of the way, and adjust the trim in high by way of adjusting the cable length (tension). You want it adjusted so it shifts crisply, and the trim ends up so the outer plate barely clears the chain when it's coming from the outermost rear sprocket. If it's adjusted perfectly it'll shift crisply and sometimes dump the chain over the side. You'll now make a final adjustment of the limit screw to prevent dumping the chain, but not so far that it's affecting the trim.