I bought a Calfee Tetra Tetra tandem in March '07 and have been very happy with it overall. I have Durace shifters and front derailleur, XTR rear derailleur, and yes, IRD 11/34 rear cassette. We have now put about 765 miles on it and still am trying to get the shifting right.
After determining that the cable housings were too short and the cables were sticking, new housings and cables were installed which improved the shifting somewhat at 600 miles. It no longer threw the chain off the small chainring onto the frame, which it did 5 times before, even with mulitiple derailleur adjustments.
What is working well: The chain goes on the large chainring very well on upshifts.
What is working some of the time: Downshifts ok from the large ring to the medium chainring.
What is not: The chain seems to "skate" much too often when going from the middle to the small chain ring, and from the small to the middle chainring. The pedals seem to freewheel when in this mode. It does appear that the chain is in a gear on the rear cassette, but just doesn't quite get in the grooves on the small and midside chain rings. Once in a while it also skates from the large ring to the medium.
Also, when shifting from the small ring to the medium chain ring, I have to push the shifter twice to make it go on the ring. It does go easier to the small ring from the medium but again, sometimes skates and I have a hard time getting it to catch.
The rear cassette shifting on upshifts goes fine, but on downshifts there is slipping and trying to find the right gear with the resultant gear noise as it strives to find the correct rear gear.
Is this a cable problem, front derailleur problem, bent chain link(s), possible (but hard to believe,), captain error? I am trying to be conscious of location of chain in rear cassette before shifting so as to avoid extreme chain angles while shifting.
Thanks for your input! I am going to TTR on Thursday and hope to get this nailed down.