Originally Posted by
stevetone
Also, the crank arm length difference of 2.5mm equals 5mm of change rotationally (2.5 at top, 2.5 at bottom).
I originally learned (i.e., forced myself) to adapt to having the 170mm cranks on my single bikes, 165mm on my fixed gear, and the 175mm on the tandem per tandem lore. However, as the body aged I found myself to be less tolerant of the 175mm cranks on the tandem and moved back to 170mm in the fall of '06. It made a HUGE difference in terms of being able to spin a more efficient cadence and reducing fatigue on long distances or mountain riding.
I'm now a strong advocate of captains & stokers using the same length cranks on road tandems and road bikes.