I have a daVinci tandem with quad chain rings (12-18-24-30). This is a great steel-frame ride for my wife and I. Ever since chain suck damaged the FD (required replacement) I've been working with my LBS to find a replacement as the original is no longer available. Basically, I need a triple FD, either braze on (I use an adapter) or clamp-on. The shifters are Campy Ergo 10 spd with a 10 spd chain. Braze-on would be preferred as the clamp-ons may not have enought travel to get to the 30t chain ring.
Here's the unusual problem: the FD are typically designed with a ramp that assists the chain at the beginning of the shift. This works great when the radius difference between the chain rings allows the ramp to engage first. In my situation the chain rings are so close together that the flat part of the inner cage initiates the shift and as the FD moves outward the ramp on the inner cage tends to kick the chain off the outside of the 30t chain ring.
We've done tons of tweaking and I can almost get by if I avoid shifting 24t to 30t in the smaller cogs, but that's not a long term solution. I'm going to do some additional experimentation (raising the FD beyond what is normal for example), but the real solution is a FD with a different ramp profile.
Any and all suggestions will be appreciated.