let me begin by saying that i like shimano hubs. i like the serviceability, have all the tools to rebuild, and only once had a failure (flange broke) in many miles. i'm also very loyal to what i know. that's a little background.
i just bought an early 80's santana road tandem, and i'm interested in building a set of wheels for it. i'm leaning towards 36h velocity fusion rims to be our lighter, faster touring and day tripping set (then later building something beefier for loaded touring). i definately want to use disc brakes on this bike, so when i noticed that shimano does not make a disc tandem hub, i'm looking at the white m16. then i stumbled upon a thread in this forum (i think) where the discussion was about the difference between this hub and their mountain hub. i digested my white industries literature and now believe that difference is 1. longer axle, and 2. more casting where the rotor attaches (corresponds to the longer axle). the distance between flanges is the same, just more centered ('cause the axle is longer).
so then i go looking at the difference between the xt shimano non-disc hubs and think i'm seeing a pattern. so for hundreds of dollars less than a pair of m16's, i'm thinking about buying a pair of xt m756 hubs, putting a longer axle in the rear, making a spacer for the disc rotor and using longer disc attachment bolts.
any thoughts about this?