Originally Posted by
Chris_W
The Dura Ace triple middle ring (39 tooth) will only work on cranks that have no mounting posts for the inner ring, like the new Ultegra-level tandem cranks, or the Ultegra or Dura Ace single-bike triple cranks. Therefore, it probably wont work; even if it does, then the only ring that you can mount onto it for the inner ring is Shimano's 30 tooth (the BCD has to be the odd 92 mm size). Since you therefore probably cannot use the matching middle ring, it probably doesn't matter exactly which outer Dura Ace ring you use. I believe we are using the 53 tooth double version, which works really well.
Boy, am I glad I am happy with using TA middle and inner rings, and do not have to figure this out.
I still don't know, however, with transitioning from a 30t [53-42-30] to a 28t inner ring, what is the largest size middle ring to use (39t?), and with a 39t middle ring, what is the largest outer ring that could be used?