Confused about short, medium, and long cage rear derailleur capacity!



hd reynolds said:
Well that's just the problem with a 'know it all' - you think you know better than what the manufacturer intended it to be. Like I said, it MAY work but is not recommended - because it is not the optimal component for the intended use. It may result in miss shifts, shorter component life and alike. Misguided information just because you've done it does not mean you are right.
Some just need to get their head out of their aZZ too. The paralleogram of the short and medium is the same, and that is what determines big cog capability. Cage length is about chain wrap. AFWIW dunce, I'm not the only one having done it.It's fairly common practice.
 
boudreaux said:
Some just need to get their head out of their aZZ too. The paralleogram of the short and medium is the same, and that is what determines big cog capability. Cage length is about chain wrap. AFWIW dunce, I'm not the only one having done it.It's fairly common practice.
*what a big ***** Cog compatibility is not only determined by the parallelogram. Any half AZZ should know that big cog compatibility is determined by both parallelogram articulation and cage length and not exclusively by the parallelogram. Besides, if you look closely at the 2005 campy specs. sheet you will see that the parallelogram of the short medium and long cage have different tolerances.

Fairly common practice it may be but it still does not mean it is right. You must be one of them conformist who will follow another IDIOT because he's practicing it.
 
hd reynolds said:
A short cage campy "MAY" theoretically work with a 29 but is not recommended by Campy. The short cage is only recommended for cogs up to 26. You need a medium for a 29.
Well, if you were starting from "scratch", buying the medium RD would be the right thing to do. OTOH, if you already own the short version, it's worth a try. IME, max cog size can most often be exceeded by 2-3 teeth, depending on a few variables including the right side rear dropout. The manufacturers (all of 'em, not just Campy) spec on this is usually _very_ conservative in order to take into account differences in rear dropouts, slightly mis-sized chains, etc.
 
hd reynolds said:
*what a big ***** Cog compatibility is not only determined by the parallelogram. Any half AZZ should know that big cog compatibility is determined by both parallelogram articulation and cage length and not exclusively by the parallelogram. Besides, if you look closely at the 2005 campy specs. sheet you will see that the parallelogram of the short medium and long cage have different tolerances.

Fairly common practice it may be but it still does not mean it is right. You must be one of them conformist who will follow another IDIOT because he's practicing it.
'tolerances' :rolleyes: Link me to that Willis. I couldn't find it.