I just popped a spoke on my rear wheel. I was going pretty quick, the spoke got caught in my chain, and wrecked my rear derailleur. It's completely bent up, missing a gear, etc.
I have a full Shimano Ultegra group, double in front, 9-speed in the rear. I need to buy a replacement derailleur, and I see a bunch on EBay, but I have some questions first:
1) Some of the derailleurs I see listed are described as "triples". I thought all 9-speed Ultegra rear derailleurs were the same. Does it matter if my front gear is a double or a triple? Why would this affect which model or rear derailleur I buy?
2) What is the difference between long-cage and short-cage derailleur? How do I tell which one I currently have? Does one perform better than the other?
3) Is there a model numer on my derailleur somewhere that I'm just not seeing? A model number would make things a lot simpler.