Will a short cage 10 speed Chorus rear derailleur work okay with 12-27 and 50/34

[Oxford_Guy]

Will a short cage 10 speed pre-2010 Campagnolo Chorus rear derailleur work okay with a Centaur 12-27 cassette and compact 50/34 chain set without any drama? I try not to cross chain small-small or large-large, but don't want a disaster if that happens.

I think Campagnolo say a max cog size of 26T, but that was before the 12-27 cassette was available. Chain wrap would be 31 teeth, which I think may be slightly over spec.

[pdmtong]

I have used a short cage RD with a 50-34 and 13-29 no issue (yes avoid the 50-29).

[Oxford_Guy]

I have used a short cage RD with a 50-34 and 13-29 no issue (yes avoid the 50-29).

If I accidentally went into 50-27 would that be okay, though? I wouldn't want to make a habit of it, but it could happen.

[makoti]

If I accidentally went into 50-27 would that be okay, though? I wouldn't want to make a habit of it, but it could happen.

It won't break anything if you get into the gear once in a while. Ask me how I know. ;)

[choke]

Yes. I have a 50/34 and a 12-29 with a short cage Chorus and it works fine....all the gears.

[pdmtong]

If I accidentally went into 50-27 would that be okay, though? I wouldn't want to make a habit of it, but it could happen.
In my case the 50-29 did not result in any risk of destruction. There are chaniline and chainstay nuances here which I am not equipped to advise on that may create risk for you. However for me, it was actually fine for all gear using the short cage.

[Steve in SLO]

Another positive experience here. Just make sure your chain length is good. It obviously needs to allow you to reach big-big as well as not have too much slack/slap at the small-small.

[Dave]

It depends on your chainstay length. A perfect length can gain at least 2T of wrap, compared to the worst case. 1 inch of chain equals 4T of wrap, so any change adds or subtracts 4T at a time.

[Oxford_Guy]

It depends on your chainstay length. A perfect length can gain at least 2T of wrap, compared to the worst case. 1 inch of chain equals 4T of wrap, so any change adds or subtracts 4T at a time.

I think my chain stays are 420mm, which I guess is a little on the long side for a road bike, hopefully that's not going to be a problem? I don't need to go up to a 29T cog, though, 12-27 is just fine.

[Ralph]

Nothing keeping you from installing the chain a tad on the long side.....until you get it figured out. If small to small too sloppy, and big to big wraps up with chain to spare....then take a couple links out. Otherwise....riding with small to small a tad sloppy doesn't hurt anything....you don't ride that way anyway. Assuming the upper pulley clears the large cog when you go there. if not, adjust with B screw, and if that not enough, take the 2 links out....it will pull the pulley back out of way. But start out with a generous length chain. Easier to take links out, then put back in with another quik link.

[weaponsgrade]

I've also run a 50/34, short cage RD, and 29T cog without problem. I avoid the small-small and big-big combos. I tested the big-big in the stand. It didn't look pretty but at least it wouldn't rip the RD off if I happened to accidentally shift into it.

[Oxford_Guy]

So from the sound of it, short cage and just 12-27 and 50/34 should be just fine. Hope so!

[Dave]

Long chainstays are not the issue, it's the specific length, relative to the chain length formula.

Here's a link to the formula, that uses inch dimensions. If you put in 15.95 inch or 405mm, it comes out to nearly a perfect 54 inch chain length, but still rounds up to 55 inches. I'm thinking that you get the maximum extra wrap with a length like this, rather than something that comes out to 54.9 inches and still rounds up to the same 55 inches. The 55 inches just barely works.

If you put in 420mm or 16.535 inches, the result is a 55.17 inch chain that rounds to 56, so there should be plenty of extra length.

http://www.machinehead-software.co.uk/bike/chain_length/chainlengthcalc.html

[Oxford_Guy]

Long chainstays are not the issue, it's the specific length, relative to the chain length formula.

Here's a link to the formula, that uses inch dimensions. If you put in 15.95 inch or 405mm, it comes out to nearly a perfect 54 inch chain length, but still rounds up to 55 inches. I'm thinking that you get the maximum extra wrap with a length like this, rather than something that comes out to 54.9 inches and still rounds up to the same 55 inches. The 55 inches just barely works.

If you put in 420mm or 16.535 inches, the result is a 55.17 inch chain that rounds to 56, so there should be plenty of extra length.

http://www.machinehead-software.co.uk/bike/chain_length/chainlengthcalc.html

Trying to get my head around this, but are you saying that in theory 420mm chain stays should be fine, regarding the chain length/wrap?

[oldpotatoe]

Will a short cage 10 speed pre-2010 Campagnolo Chorus rear derailleur work okay with a Centaur 12-27 cassette and compact 50/34 chain set without any drama? I try not to cross chain small-small or large-large, but don't want a disaster if that happens.

I think Campagnolo say a max cog size of 26T, but that was before the 12-27 cassette was available. Chain wrap would be 31 teeth, which I think may be slightly over spec.

Not true..13-29 and then 12-30 for Campag 10s, 'standard' cage length..just make sure chain length is 'proper', just enough for big-big combo.

[Ralph]

There is (was) a 12-27 10's Centaur. Largest 3 cogs pined together same as the 12-30. 12-13-14-15-17-19-21-23-25-27. Except for the 3 pined cogs, uses 2.5 MM spacers thru out. Same as the 12-30. I've got the spec sheet that comes with both. They are different than earlier 10's Centaurs. Much lighter for some reason. My 12-30 weighs same or slightly less than an older loose cog 10's 13-26.

[Dave]

Trying to get my head around this, but are you saying that in theory 420mm chain stays should be fine, regarding the chain length/wrap?

Yes, with a 56 inch chain.

[oldpotatoe]

Trying to get my head around this, but are you saying that in theory 420mm chain stays should be fine, regarding the chain length/wrap?

We had a demo Moots with Chorus 'normal' cage, 10s, compact, 13-29 for a long time and never had any problem..

[Oxford_Guy]

Not true..13-29 and then 12-30 for Campag 10s, 'standard' cage length..just make sure chain length is 'proper', just enough for big-big combo.

Even for early pre-2010 10-speed derailleurs? Don't think so!

Pretty sure 12-30 would require a medium. Anyway, all I want to know is if it will work with 12-27

[Oxford_Guy]

There is (was) a 12-27 10's Centaur. Largest 3 cogs pined together same as the 12-30. 12-13-14-15-17-19-21-23-25-27. Except for the 3 pined cogs, uses 2.5 MM spacers thru out. Same as the 12-30. I've got the spec sheet that comes with both. They are different than earlier 10's Centaurs. Much lighter for some reason. My 12-30 weighs same or slightly less than an older loose cog 10's 13-26.

That's the cassette I want to use, managed to get a few of the Centaur 12-27 10 speed cassettes at a good price.

[oldpotatoe]

Even for early pre-2010 10-speed derailleurs? Don't think so!

Pretty sure 12-30 would require a medium. Anyway, all I want to know is if it will work with 12-27

Ah, nope..as soon as the 12-30 came out, we put that one..same rear der...worked for a 13-29, worked for a 12-30..BTW..2009 Chorus went to 11s, Centaur, Veloce still 10s..'2010'...'pre' 2010' Chorus 10s..13-29 and 12-30, compact, no problem on the 'demo' Moots woth 'standard(short) rear der..12-27, no problem at all.