Replacing Derailleur

[VeloVT]

you need to know if your bike requires a braze on derailleur or a clamp on derailleur... you'll be able to get either type in any of the groups though. It also makes a difference if you have a double or triple crankset (triple requires a longer der?), and **I think** (someone may have to correct me here) it makes some difference how many speeds you are running in back, because some der's are narrower/wider to accomodate different chain angles (that result from different rear-cog spacing) without rubbing. Not sure about this last though.

you should be able to find something compatible with your bike in each of the groups, but not every derailleur in each group will be an ideal choice, if that makes sense.

chain dropping (especially on a hill) can be related to adjustment (so it may not be something inherently wrong with your derailleur) and it can also very much be related to shifting technique. you really have to let up to get a good downshift while climbing. that said, I have a 105 triple fd on one of my bikes and, while it doesn't drop my chain when it's adjusted properly, it's also just a little sluggish and sloppy compared to my Ultegra triple fd.