Triple to Double, New Rear Derailleur?
 

I'm thinking of swapping my triple for double (carbon). I've got a long cage DA triple rear derailleur. If I have to replace it with a short cage I'm not going to do it at all given that I've spent a ridiculous amount swapping components, trying one way then the other way with my credit card leading the way. e.g. not too long ago I had a short cage derailleur with my triple and needed to swap it with the current derailleur. I'm not going to go out and buy another one. Gotta draw the line somewhere.

...and no I don't still have the other one.

Thanks!

There isn't any need for a new RD, you will be fine. Just make sure you get the chain length right.

Oh My! Think of all that extra weight you'll be pushing around. You'd better change it out right away!


Just kidding. I would wait until the killer deal came around that coincided with some extra cash in pocket. Maybe someone else is going from double to triple and would trade. Certainly no hurry this time, not like needing the long cage for the triple.

Good to know, thanks. Ya know as ridiculous as it is, the weight issue will gnaw at me to the point that I'll have to make the switch - and of course, I can't get lesser than a DA:o Thankfully there will be no functionality issues with keeping it for awhile.

longer rear derailler cages are useful to take up more chain slack. So when you go from a double to a triple, you probably need to update to a long-cage, because a short-cage rear der likely can't take up enough chain slack for the triple to work.
Going the other way, you can use a long-cage rear derailler with a double-chainring drivetrain; you simply won't be using all of its chainwrap capacity.
However, the D/A long-cage rear derailler is plenty light. For comparison:
Dura-Ace long-cage: 212g
Ultegra short-cage: 209g

Even if you were to update to a Dura-Ace short-cage rear derailler, it comes in at 180g. And the difference between 180g and 212g, my friends, is 7% of a pound.

So, if there's any gnawing to be done, it's the more rational part of your brain against the paranoid part of your brain, for worrying about the "extra weight" :D

don't need it.

I suppose I might allow 32g. Yeah, It'll be ok... :o

It's amazing how marketing can be so effective that even when a consumer knows he's wasting his time and money, he can't help but do so.

How true a statement that is - However, ultimately we only have ourselves to blame. So being, I publicly state that I'll keep what I have. Moreover, I'm not going to upgrade my other bike from 105 shifters to Ultegra as I had planned to do, because the reality is that in my experience the 105's work flawlessly, with no perceptible differences in performance even when compared to my Dura-Ace shifters.

Having said that, I'm going to grab my bikes as they are and find a cave where I'll be entirely free of the influence of advertising! :D