Chris_W

As for mounting a triple chainring to the Hollowgram cranks, then it should be no problem to just use Cannondale's 130mm BCD spider plus a Tripleizer ring in place of the inner ring (I believe TA Specialites still makes them). You'd then have a 74mm BCD for the inner ring.

This would basically the same as the setup on the Shimano R603 tandem / Ultegra 6703 cranks (except that the middle ring on those gives a 92mm BCD for the inner). You'd have to check that there is frame clearance for the inner ring (probably no problem with such a small ring, and you could go with something smaller than a 30 tooth if that helps) and you may be limited to using only the innermost half of the cassette with the small ring due to chainline / cross-chaining, but that is all you need the small ring for anyway.

Using eccentric BBs should remove part of the problem with BB30. Most problems with BB30 are due to the BB shell in some frames not being quite perfect, so the bearings don't fit as well as they need to. The tolerance should be easier to achieve inside an eccentric BB, and if it isn't right then you can just swap the eccentric out for another one. This is why some manufacturers are now using the PressFit 30 instead of the pure BB30 (and Specialized uses the similar OSBB system on their S-Works road frames), so that the bearings don't press directly into the frame (it's the same reason why Chris King criticized the design of integrated headsets for so long). This may therefore be why they use a second eccentric for the stoker's BB, although a PressFit 30 would surely have been a lighter solution.

My personal opinion is that if Shimano's 24mm axles are stiff enough for Mark Cavendish's and Bradley Wiggin's bikes (they, and the rest of Team Sky, were normally using Dura Ace 7800 cranks), then there is no need for me, or almost any other tandem teams, to need crank axles any stiffer than that. I do believe that the hollow 24mm axles are stiffer than the old square taper setups, which is why I wouldn't consider square taper axle cranks for our tandem. Our current solution is to use a pair of Shimano 105, 5603, single-bike cranks on the tandem - using only the middle and inner rings (42-26) for the drive chain, and the timing ring in the outer position. This gives us a broader range of crank lengths to choose from, so we can have our preferred 165mm cranks front and rear. Someone recently posted a thread here showing how you can have this kind of setup while still keeping an outer chainring as well as a timing ring outside of that. With all these options, then there really is no need for special tandem cranksets.