I have an Ultegra 9 speed drive train with a 53-39 up front and a 12-27 in the back. On the 4th cog gear from the smallest I am having shifting problems. When I shift from the 3 to 4 (smaller to bigger cog) it doesn't want to shift. If I make adjustements so it will shift, then I have the same problem going from 5 to 4. I always have to shift twice in one direction then shift back once to get to that gear. I recently got a new wheelset, cassette, and chain and I still have the same problem. Is it the wider spacing in the 12-27 cassette that is causing the problem. BTW everything is Shimano...the chain is Ultegra.