SRAM Red 11-28 cassette, up-shifting not smooth
I hope someone can help me. I recently changed my cassette to a SRAM red 11-28, 10-speed, which in combination with my newly added 50-34 compact double provides some excellent gearing options. When I changed the cassette, I also changed the chain with a new dura ace. The rest of my components are Shimano Ultegra. 50% of the time when I upshift, the chain doesn't quite go into gear on the cassette. This causes a lot of irritating noise which can only be fixed by waiting for the chain to find the gear. This takes about 20 seconds or more. Another solution when this happens, I simply upshift to the next gear and then downshift one gear. What is happening here? Is it the rear derailer? I was planning on changing the RD to a SRAM, but I read that this won't work because of incompatibility. What if I changed the chain to a SRAM? Or is it possible that my mechanic simply didn't adjust the derailer properly? Thanks for helping.