Originally Posted by jnbrown
I could also just get a clamp on Campy derailleur. The thing I am not sure of is if the derailleur will reach out far enough since the chainrings are further out on a tandem than on a single by 5mm or so.
I thought we discussed the nuances of front derailleur spacing in a previous thread that you started on chain lines?
As I noted, if you're messing around with 160mm rear spacing and are attempting to compensate the chain line for the added cassette off-set you'll need to search out one of Santana's Far-Out front derailleur clamps; they are the only ones that move the front derailleur out the extra 5mm that you are looking for.
For 145mm or narrower-spaced tandems, so long as the clamp will fit around the rear seat tube it doesn't matter whose clamp you use; they're universally compatible with front derailleurs made without the integrated clamp that were designed to bolt to frames with brazed-on clamps, i.e., 'braze-on derailleurs". The clamps marketed by Campy, Shimano, FSA and others all align to the same off-set used for standard front derailleur mountings... and that's typically 'good enough' for tandems with up to 145mm rear spacing. The only difference in these various clamps are cosmetic so if you're a Campy purist then, by all means, get one of the Campy FD clamps.
Again, for 160mm rear spacing, when Santana switched from bar-end and downtube shifting to STI for their triple-equipped tandems -- first using Glenn Erickson's Gizzmo on DuraAce STI that was not made for triples -- and then with the 105 Triple when it became available, the front derailleur shifting that had previously been good was now less than good. So, they came up with the special 'Far-Out' front derailleur clamp that moved the front derailleur 5mm further away from the frame to solve the balky and problematic front shifting on their '99 and up models.
Also as previously noted, the other thing you need to be mindful of when using the 'Far-Out' front derailleur clamp is the need to have either an off-set or very wide rear spindle that will allow the right side drive crank to take advantage of the extra 5mm of front chainline off-set: I believe Santana spec's something like a 127mm or 129mm wide spindle in this regard depending on when it was produced. For reference purposes, we use a 111mm for Debbie in back and I have a 108mm spindle on our 145mm rear-spaced tandems, i.e., the preference for narrow tread is one of the reasons we decided to replace our first tandem -- a '95/96 Santana Arriva -- after 8 months.