I've got a 12-23 Dura Ace (CS-7700) on an Easton EA90 SL rear wheel. The shifting was perfect to begin with. I put an Ultegra 12-27 (CS-6500) on my Velomax R1 rear wheel. The shifting was immediately rough and I was not able to shift it into the lowest gear (the 27). I tried playing with the rear barrel adjuster to no avail. I put my Easton back on, and got the shifting to about 95% the smoothness it had previously been it set at. I'm at a loss as to how to get these two sets of gears working without having to mess with the alignment.
Is this even possible?