Took out my cross bike for a shakedown yesterday. When I am in the small chain ring and standing and really stomping up hills, the chain was jumping around on the cassette seeming to shift on its own. Otherwise, when I am sitting or riding a flat the system shifts flawlessly. If I am in my big ring up front, and standing on a climb, the chain does not skip around on the cassette. My theory is that the chain might be too long. When I put the chain on the big ring in front and the smallest cog in back, the pulleys are not perpendicular to the ground, but instead at about a 65% angle. If I shorten the chain a few links, making the pulley cage perpendicular to the ground, might that solve the problem?