My wife and I went out for a ride a couple weekends ago at Terry Hershey park and halfway through, I was downshifting from my big ring to my small ring and my chain fell off! I've adjusted the Limit screws several times, but it still doesn't perform like I want it to. Keep in mind, I have low end components... Sora in the front and Tiagra in the back - which is probably part of the problem. I really want to replace my front derailleur and was wondering what I need to look for when doing so. I believe i need a clamp on, but aside from that is there anything else that I need to look for when buying one? Also, do I need to change anything else when upgrading?