When I'm on the middle of the 3 gears (in the front...I forget the 'technical' name for it...I'm a newbie, so shoot me ), the bike seems to want to shift itself. I'm guessing it's the tension on the shifter cable, and the bike store guy seems to think the same. This being said, is there anything else that can cause this? The bike is somewhat new (2 months, although I've pounded it ) so I don't think it's an incorrectly installed derailleur or something. Any help would be appreciated.