I have about had it with this problem. I've taken my bike in to the LBS twice to have the front derailleur adjusted after dropping the chain on the 53-39 shift multiple times on 2 different group rides. The problem is not isolated to shifting while the back cog is on the biggest, or next to biggest. I can be anywhere from the largest cog, to the 6th largest cog, and it'll drop. I'm not shifting under pedal power, just a light spin. I have a KMC master link on a shimano chain (which I've posted about before) and I don't know if that has anything to do with it. Today on the group ride I dropped it FOUR times. This makes for me getting dropped from the pack and riding alone. The fact that I ride alone kinda defeats the purpose of going on a group ride, so it really kinda pisses me off that this is a problem on a bike with 225 miles on it, that I've had less than 8 weeks.
Anyway, just looking for anyone that might have advice as to anything I can do to fix this.
Info: 2005 Cannondale R700, truVativ crank/chainrings that came on it, 105 Front Derailleur.
Are you dropping on large-to-small, or small-to-large shifts? Suggest http://www.parktool.com/repair/readhowto.asp?id=75 as a good guide to tuning up that front derailleur. It can be a number of things, from incorrect limit screw settings (most probable), to incorrect derailleur alignment (too high and/or not straight).