Campagnolo. Changing to compact

[trj977]

I have real old school Campagnolo 10 Speed UD Carbon Chorus with a 52 / 42 chainset.
I have managed to source a second-hand compact chainset 50 / 34 and compact front derailleur these are also 10 Speed UD Carbon Chorus.
My question is, will the rear derailleur be able to handle the increased difference in the rings eg 16 vs 10. I have attached a photograph of the derailleur in case it helps. I am afraid I don't know if it is a short cage?

 

[Smokin Joe]

It is a short cage and it will handle it no problem.

 

[trj977]

Many thanks for your help. My knees will greatly appreciate your knowledge ;-)

 

[Graeme_FK]

I have real old school Campagnolo 10 Speed UD Carbon Chorus with a 52 / 42 chainset.
I have managed to source a second-hand compact chainset 50 / 34 and compact front derailleur these are also 10 Speed UD Carbon Chorus.
My question is, will the rear derailleur be able to handle the increased difference in the rings eg 16 vs 10. I have attached a photograph of the derailleur in case it helps. I am afraid I don't know if it is a short cage?

Smokin' Joe's answer is not quite as complete as it (maybe) needs to be. Not so much thinking of the OP but of others looking for similar info but with maybe slightly different circumstances ...

The short cage RD will be OK up to a certain number of teeth difference overall ...

Campagnolo 2007-version Chorus short cage RDs (that's what you have) will reliably and safely handle a total of 31T difference, with a 27T max sprocket & a minimum sprocket size of 11T, given a max sprocket difference of 16T, provided the frame and hanger dimensions match Campagnolo's specification.

Before this post is swamped with "my mates got x and y and that works fine" type posts contradicting the above, note the two caveats "reliably and safely" and "provided the frame ...." - Yes, some users have managed to squeeze more range out of these RDs in specific circumstances and some have actually (especially on older frames) not managed to get quite as much range ... but these users are operating outside of the "safe" specification and what works in their particular circumstance may and may not work for the OP.

So - what do the numbers mean?

Total tooth difference is the difference at the chainset (50-34 = 16) plus the difference at the cassette - so in the case of the very common 12-25, that's 13T.
16+13 = 29 is your tooth difference - within the RDs capacity and the total difference at the cassette is less than 16 so you are OK.

In the quest for lower gears, though, you might be tempted to fit one of the recently introduced Campagnolo 12-27 or 12-30T cassettes. 12-27 will be marginal but should be OK given the proviso about frame and hanger spec (you may need to pay attention to chain length - very important) and to the "H" screw adjustment (to get good and correct shifting across the range), the 12-30 you won't be able to use.

Full technical details (including frame and hanger specs which have not changed since 2007, at least) are available in the relevant Campagnolo technical manuals all of which are available at www.campagnolo.com

HTH
Graeme
Campagnolo main UK SC

 

[trj977]

Graeme such a complete explanation is very much appreciated.
Unfortunately having just checked, I have a 13 - 28 cassette which would put me outside the 27T max, this appears to work fine at the moment? However I note the two caveats "reliably and safely" and "provided the frame ....". Looking at the link the only reference to 10 Speed I found was on this page:

http://www.campagnolo.com/media/fil... rear derailleur - Campagnolo_REV00_07_13.pdf

If it is the correct page and I am reading it correctly, absolutely no guarantee of either, it seems that the Max Sprocket could be 30T?

Not questioning your obvious expertise but more to increase my knowledge, how do you know it is 2007 Chorus, I thought it was older?

Just in case you are wondering the frame is a De Rose Merak, early version with carbon rear triangle and forks. Please note that I am not asking you to comment on the frame and hanger spec it si just for info.

Many thanks

Tom

 

[Graeme_FK]

Hi Tom

The document that you have referenced refers to the current production 10s RDs that do have a higher capacity than the older versions.

Your Chorus RD *may* be older, TBH. The last revision of that RD was in 2007, though. The design with the carbon outer plate on the parallelogram actually originated in 2004, so yours is quite possibly older - the specifications are the same as far as max tooth capacity etc are concerned, however.

If you are succesfully running 13-28, that may be because the DeRosa hanger is slightly longer than Campagnolo's spec, or the relative angular positions of where the top pivot bolt is, and where the wheel centre is, differ slightly from Campag's spec. The issue of max sprocket size normally comes up on the "small to big" combination, where the tops of the teeth on the top jockey can catch the tops of the teeth on the biggest sprocket and that interference between the two can't be adjusted out.

With 13-28 you have 15 difference there, with the 50-34 you'll have 16 difference, total 31T so that's right on the tooth difference limit though over the max sprocket size (theoretically) ... but you could be *just* OK. Hard to say for sure because of the max sprocket size element, without the bike in front of me.

You may need to crop the chain a bit, as when on 34 x 13 you may not have enough tension on the chain - see the chain length spec on the Campag website - the clearance they recommend now is the same as for derailleurs of the same vintage as yours. There is a caveat however (as you might have guessed) ... you need to ensure that if you shorten the chain to get the correct length on the small to small combination, there is enough chain to allow the shift up to big-to-big. If you were inside the spec in every regard, this would not be an issue but as you are right at the edge, or arguably just over the edge of the spec with the 28T, it would be a very good idea to check this.

Bear in mind you need slightly more chain to actually "make" the shift than when you are actually in gear, as there has to be enough to let the chain "climb over" the teeth on the big sprocket / chainring (depending whether you are shifting at front or rear).

If you are forced into a choice - chain slightly too long so using 34 x 13 causes the two "runs" of chain to touch slightly under the RD, or chain too short - so not enough to make the big-to-big shift, go for the former. Too long is always a better bet than too short, where chains are concerned, and provided it's not to excess.

The reasoning for that is this - you are aware I am sure that we advise excessive "crossing" of the chain is bad practice anyway (so one should avoid using big to big and small to small) but these gears do get "grabbed" in extremis sometimes ... if the chain is a tad too long, it makes a racket in small-small as the two runs of chain rattle over each other under the RD - and if you ride in this combination incessantly, it would eventually damage things - but this is better than not having enough chain to make the big to big shift. In this case if there isn't enough chain, it can destroy the rear hanger, rear derailleur and usually demolishes he rear wheel (as the gear fails and swings into it) and in doing so also twists the chain so costing you a chain and perhaps cassette (depending on the relative states of wear). If you are really unlucky, it can damage the frame too.

So, on balance - be careful ... :-)

Graeme

 

[ColinJ]

Obviously Graeme knows what he is talking about so heed his warnings!

Having said that, I think I have exceeded the nominal capacity of my old Campagnolo triple groupset but it does work on my bike...

I wanted really low gears for some of the ultra-steep climbs I tackle round here so I replaced the 30-tooth little ring with a 26, and replaced the original 12-23 cassette with a 14-28. The bike has a 52-tooth big ring and a long-cage rear mech.

It is possible to get the chain length such that all the slack is taken up in little-little, but the system can survive big-big. A friend told me not to worry about big-big because you would never ride in that gear, but I wanted to make sure that nothing would break if I selected it. I went for a ride yesterday evening and selected big-big twice when distracted! (It happened because I am getting fitter and forget that I am sometimes now on the middle ring where I used to be on the granny ring, and on the big ring where I used to be on the middle ring.)

 

[Smokin Joe]

Smokin' Joe's answer is not quite as complete as it (maybe) needs to be. Not so much thinking of the OP but of others looking for similar info but with maybe slightly different circumstances ...

The short cage RD will be OK up to a certain number of teeth difference overall ...

Campagnolo 2007-version Chorus short cage RDs (that's what you have) will reliably and safely handle a total of 31T difference, with a 27T max sprocket & a minimum sprocket size of 11T, given a max sprocket difference of 16T, provided the frame and hanger dimensions match Campagnolo's specification.

Before this post is swamped with "my mates got x and y and that works fine" type posts contradicting the above, note the two caveats "reliably and safely" and "provided the frame ...." - Yes, some users have managed to squeeze more range out of these RDs in specific circumstances and some have actually (especially on older frames) not managed to get quite as much range ... but these users are operating outside of the "safe" specification and what works in their particular circumstance may and may not work for the OP.

So - what do the numbers mean?

Total tooth difference is the difference at the chainset (50-34 = 16) plus the difference at the cassette - so in the case of the very common 12-25, that's 13T.
16+13 = 29 is your tooth difference - within the RDs capacity and the total difference at the cassette is less than 16 so you are OK.

In the quest for lower gears, though, you might be tempted to fit one of the recently introduced Campagnolo 12-27 or 12-30T cassettes. 12-27 will be marginal but should be OK given the proviso about frame and hanger spec (you may need to pay attention to chain length - very important) and to the "H" screw adjustment (to get good and correct shifting across the range), the 12-30 you won't be able to use.

Full technical details (including frame and hanger specs which have not changed since 2007, at least) are available in the relevant Campagnolo technical manuals all of which are available at www.campagnolo.com

HTH
Graeme
Campagnolo main UK SC

Interesting post, Graeme.

I've run that combo with Campag on a couple of bikes and now do the same with a short cage Shimano set up so I assumed it would be universal. Obviously not.

 

[trj977]

I appreciate all the input you guys have given and am very impressed by Graeme's obvious expertise. So a big thanks to all.

The plan will be to swap Front mech and chainset when I return from holiday and adjust chain length etc. accordingly. The clear and precise advice received on here has given me the confidence to attempt this.

Then if all goes well, take her out for a nervous ride!! Will let you know how I get on.

 

[trj977]

Just in case anybody was wondering.

Changed chainset and chain and all works fine even with the old Front Mech. Probably due to the fact it was a band on so I could drop it far enough.
Hills do seem better now, not any faster just easier.

Once again many thanks for all the help and advice.