Campagnolo RD-RE002M medium cage in pre 2015 11s Chorus

Discuss light weight issues concerning road bikes & parts.
upacs
Posts: 22
Joined: Fri Feb 22, 2013 9:50 am

by upacs

Hello all

I'm running a Campagnolo Chorus groupset, pre 2015, with a short cage rear derailleur (because that's all that there ever was). I would like to run a 32t casette, so I'm looking for options other than upgrading the entire groupset.

In my search I have bumped into the spare part RD-RE002M, which is a medium cage rear derailleur, here:

https://www.bike24.com/1.php?content=8; ... d%5B1%5D=1

The description says it's compatible with Chorus 11 speed, but no idea if that is the original Chorus 11s I have, or the post 2015 model. Unfortunately looking at the parts catalogue isn't helping much here. This is the relevant one for my derailleur (page 38)

https://www.campagnolo.com/media/files/ ... part_A.pdf

Does anyone know if the medium cage (RD-RE002M) would fit Chorus 11s pre 2015? or point me to where I could find this info?

Thanks all!

Bondurant
Posts: 107
Joined: Tue Mar 01, 2011 12:28 pm

by Bondurant

Hoping someone else can pitch in, I'd be interesed in knowing the answer also. All I could find was this link from Velotech but it talks about spring tension in Potenza vs. Chorus rear mechs being incompatible vs. whether this (generic?) part fits multiple mech families.
http://www.velotech-cycling.ltd.uk/camp ... l#comp-mec

by Weenie


Bondurant
Posts: 107
Joined: Tue Mar 01, 2011 12:28 pm

by Bondurant

Thinking about it, I'd be surprised that a mech cage can be compatible with both 10 speed and 11 speed as described on Bike24 due to the difference in chain widths, but maybe this difference would be too small to affect shifting.

upacs
Posts: 22
Joined: Fri Feb 22, 2013 9:50 am

by upacs

The cage doesn't interact with the chain at all, only the jockey wheels. The width between the two cage plates could have remained constant, but the jockey wheels made to have slightly thinner teeth when the jump to 11 was done, and it would still work just fine.

Total speculation on my part, just saying that it is feasible

upacs
Posts: 22
Joined: Fri Feb 22, 2013 9:50 am

by upacs

I heard back from Bike24. Apparently it's only compatible with 2015 Chorus 11 rear derailleur, not the original one circa 2008/9. Sounds rather strange to me that this part is for the original Record 10 and also newer Chorus 11 (not the older Chorus 11), but if this is what they say...

Now I'm running out of options, so time to start looking for a new groupset for 2019 :(

upacs
Posts: 22
Joined: Fri Feb 22, 2013 9:50 am

by upacs

I got a second email from Bike24:
My answer was too hasty. This cage is compatible to Chorus, Record and Super record 10 speed (first generation). But not to the 11 speed dérailleurs. So our description is not correct.
So there you have it. New grouppo time :x

bm0p700f
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by bm0p700f

I thinlk you swap the athena cage in . youll have to check the spare parts catalogue for 2009-2014 chorus the athena med cage fits.

campagowlo
Posts: 225
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by campagowlo

Would another option be a Chorus HO medium cage rear derailleur? Dont see why you need a new gruppo.

c50jim
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Location: Calgary

by c50jim

I had the same propblem back in 2015 with a Chorus group on my travel bike. In those days, you could buy an Athena rear derailleur that was compatible if you can find one NOS. In the 10 speed era, you could just swap the cage but my LBS said that didn't work with Chorus and Athena. When I was in Europe with some friends last month, one guy had tried one of the little rear derailleur extenders. That lasted one ride and broke on Maratona morning. I leant him my bike (I"ve done the Maratona three times so didn't care whether I rode with 9,000 people even though the roads are closed). The LBS in Corvara fitted him with new shifters and rear derailleur that workd fine so you don't need a whole new group.

AJS914
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by AJS914

You don't need a whole group but most of a group - shifters, front and rear derailleur.

bm0p700f
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by bm0p700f

11 athene RD's are still available. I know where to get them.

graeme_f_k
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by graeme_f_k

upacs wrote: ↑
Thu Aug 23, 2018 10:22 am
Hello all

I'm running a Campagnolo Chorus groupset, pre 2015, with a short cage rear derailleur (because that's all that there ever was). I would like to run a 32t casette, so I'm looking for options other than upgrading the entire groupset.

In my search I have bumped into the spare part RD-RE002M, which is a medium cage rear derailleur, here:

https://www.bike24.com/1.php?content=8; ... d%5B1%5D=1

The description says it's compatible with Chorus 11 speed, but no idea if that is the original Chorus 11s I have, or the post 2015 model. Unfortunately looking at the parts catalogue isn't helping much here. This is the relevant one for my derailleur (page 38)

https://www.campagnolo.com/media/files/ ... part_A.pdf

Does anyone know if the medium cage (RD-RE002M) would fit Chorus 11s pre 2015? or point me to where I could find this info?

Thanks all!
There is a fundamental misunderstanding here of cage length and what it will and won't allow a derailleur to do.

Cage length of itself only affects the total capacity of a derailleur - i.e. the difference in number of teeth that can be accommodated on the cassette, plus the same at the crankset. That's because the cage length only affects chain wrap, NOT the path that the top jockey wheel takes from the biggest sprocket to the smallest, or the size of the biggest bottom sprocket that the RD can work with. That is governed by the fundamental geometry of the derailleur and in some cases by the interaction of the upper and lower springs in the derailleur body, coupled to the geometry of the gear hanger itself.

If you take a pre 2015 Campag RD and graft on a medium cage, you will not necessarily be able to run a bigger bottom sprocket as the adjustment available in the H Screw may not be enough to change the balance of tensions between the upper and lower springs in the derailleur body to move the top jockey far enough from the cassette centre. This is because gear hangers vary in geometry (length, angular offset of the "hook", angular offset of the centre of the top pivot bolt relative to the rear wheel) and those factors affect the precise "hang" of the RD with any given combination of chain tension and upper and lower spring tensions.

Even in cases where it is theoretically possible to use a 32T sprocket with these older design RDs without the upper jockey fouling the biggest sprocket and giving enough clearance between the upper jockey and the biggest sprocket to allow a smooth change from and to the next-to-biggest sprocket to occur, the problem does not end there.

The upper jockey wheel does not track the cross-section of the cassette - instead, the geometry of the mech combined with the spring tensions means that it follows a more-or-less straight line, whilst the cross-section of the cassette is a curve - and the wider the ratios of the cassette, the more pronounced that curve is - so, a jockey wheel travelling in a more-or-less straight line will start comparatively close to the cassette at the "big" end, the clearance will increase towards the middle and decrease towards the small end.

This gives you two problems.

One - as the jockey-to-sprocket distance increases, you have more "free" chain between the jockey and the cassette sprocket you are trying to shift from or to, so more flexibility, changing the amount of overshift needed to acheive a smooth up- or downshift. That's the fundamental reason for having a B-Screw or H-Screw at all. This effect also means that play in the cassette body, jockey wheels, the hanger and / or the accuracy of alignment of the hanger all become of greater and greater importance as the that distance increases. Hence, poor hanger alignment, in terms of the actual shift, is usually evidenced by poor shifting especially in the middle of the cassette where the angular movement of the chain is least and any mis-alignment of the derailleur, resulting from a mis-alignment of the hanger, is at it's greatest.

Two - if, with a 2009-2015 RD, correctly set up on an in-spec hanger, you start at a 29 and travel to a 12, the top jockey spacing from the biggest and the smallest sprocket is about the same. If you extend the hanger or play about with it's design in order to accommodate a 32 and then adjust the H Screw to clear the 32 (both will be needed), by the time the derailleur has travelled to the 12 cog, it will be physically further away from it than it would be in a correctly set-up system, because you don't significantly change the tracking angle of the derailleur. The end result is that the derailleur does not control the chain well on the shift from the 13 to the 12 and it can over-run. Some shifts can result in the chain jamming between the top sprocket and the dropout, almost regardless of what is done (within reason) with the high limit screw.

Add in a bit of chain, sprocket and jockey wheel wear and some gunge on the cables and you have asystem that will perform badly and possibly unsafely as well. I sure don't want to be riding behind you on a climb when a gear change fluffs or in a sprint when you jam your chain between the 12 cog and the frame.

Next problem - leverage.

Fully crossed with a 55mm cage, with an average power output of a rider, we can estimate the maximum probable tension in the chain and so the angular component that is acting on the top pivot bolt and it's housing. Take the same set of numbers and fit a 72 mm cage and tranmit more torque (as you will with a bigger bottom sprocket) and that angular component increases proportionally as a result of the increased leverage of the longer cage - so failure of the upper knuckle of the RD becomes more likely. Now add a crash or two, or anything else that might potentially weaken that upper housing - do we think it's a good idea to add to the designed-for stress in that part of the RD? I think it's a lousy idea. Again, I don't want to be behind you when the upper housing fails and your RD goes into the wheel, stopping you dead in the road. And don't say "I never cross-chain" - yawn! - I've heard that a million times from guys who I see doing just that when they grab a gear in a race or sportif situation, in desperation or because they have mis-read a climb. I do it, you do it, we all do it ...

So, specifically ...

In the 2015 and later RDs, the geometry is better suited to wider cassettes (short cage will run 11-29, unlike the pre 2015s which have a max capacity of 12-29 or 11-27 but NOT 11-29, reliably) as the Embrace system changes the derailleur path from a straight line, to a curve, so keeping the top jockey closer to the cassette across it's complete width. The overall design of the derailleur is also conceived to increase the torsional rigidity of the parallelogram, to give a more stable platfirm for the cage to operate on.

HO RDs that are offered with medium cages have had the upper pivot housing modified and consequently offer a more rigid shift platform as well as being less prone to the leverage effect noted above. They also run quieter with a crossed chain on bigger bottom sprockets - which is why Campagnolo recommend HO RDs, not the pre 2015, non-HO with a medium cage grafted on (which is technically possible, in terms of the fitting of the cage) with 11-32 and in fact 11-29 as well.

Sorry it's long but hopefully reasonably clear.
I get asked about this a lot.
A Tech-Reps work is never done ...
Head Tech, Campagnolo main UK ASC

graeme_f_k
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by graeme_f_k

campagowlo wrote: ↑
Fri Aug 24, 2018 12:56 pm
Would another option be a Chorus HO medium cage rear derailleur? Dont see why you need a new gruppo.
At an absolute minimum, a new RH lever body would also be needed as the pull ratio on the 2105 and later RDs is different to the 2009-2014 RDs
EC-RE300 or EC-SR200 depending on CH / RE or SR.

The 2009-2014 hoods are not a perfect fit on the 2015-> lever bodies, though.
A Tech-Reps work is never done ...
Head Tech, Campagnolo main UK ASC

graeme_f_k
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by graeme_f_k

upacs wrote: ↑
Fri Aug 24, 2018 11:01 am
I heard back from Bike24. Apparently it's only compatible with 2015 Chorus 11 rear derailleur, not the original one circa 2008/9. Sounds rather strange to me that this part is for the original Record 10 and also newer Chorus 11 (not the older Chorus 11), but if this is what they say...

Now I'm running out of options, so time to start looking for a new groupset for 2019 :(
It's not properly compatible with 10s.

There is a designed-in twist in the cage which is absent from the corresponding 10s systems, which the jockey wheels have been re-designed to accommodate in an 11s situation, with an 11s chain. Campagnolo have never tested the 11s cages with 10s RDs / chains / cassettes because they see no need - dedicated medium and long cages are avilable to fit RE and CH 10s RDs.

Design and testing have to encompass a huge range of frame / hanger geometries, cassette and ring combinations etc so whilst individual users might get this to work, one never knows how they are defining "work", the durability of set up once wear and tear set in, or the long-term physical durability of any such arrangement - Campagnolo have a facility at Vicenza where they destruction test all of those things and a vast array of test bikes that groupsets of various specs are built onto, for real-world testing after all the CAD and FEA is done with and parts are prototyped. The teams and an array of trusted amateur / former pro riders also contribute to real-world testing and feedback.
A Tech-Reps work is never done ...
Head Tech, Campagnolo main UK ASC

upacs
Posts: 22
Joined: Fri Feb 22, 2013 9:50 am

by upacs

bm0p700f wrote: ↑
Fri Aug 24, 2018 12:47 pm
I thinlk you swap the athena cage in . youll have to check the spare parts catalogue for 2009-2014 chorus the athena med cage fits.
Good tip! I'll look into that, hopefully it fits and the part can also be found!
campagowlo wrote: ↑
Fri Aug 24, 2018 12:56 pm
Would another option be a Chorus HO medium cage rear derailleur? Dont see why you need a new gruppo.
The Chorus HO derailleur uses a new pull ratio, introduced in 2015. To use a Chorus HO I would need to also get new shifters, and a new front derailleur. :cry:
AJS914 wrote: ↑
Fri Aug 24, 2018 2:54 pm
You don't need a whole group but most of a group - shifters, front and rear derailleur.
You are of course correct. This is what I mean by new grouppo, but you are right, new groupset includes brakes, crankset, chain, casette as well as derailleurs and shifters, which I don't need
bm0p700f wrote: ↑
Fri Aug 24, 2018 4:05 pm
11 athene RD's are still available. I know where to get them.
Please share! I've been looking for the Athena 11 rear derailleur with mid cage, but it doesn't seem to be available anywhere. Only the short cage
graeme_f_k wrote: ↑
Sat Aug 25, 2018 2:08 am
There is a fundamental misunderstanding...
Wow, first my thanks for the detailed post.

I understand what you describe, but you'll also find that us earthlings are often willing to compromise on shift quality if the benefit outweighs it. Personally I've had to resort to using a rear derailleur hanger extension to accomodate a 32t sprocket. It's far from ideal, shifting quality is compromised, but worst of all, the cage is not long enough to keep tension on the chain when on the small ring and smaller sprockets. The last of these points makes this setup unsustainable. But as things stand right now, I must run a 32t at the back or else I won't be able to complete some of the rides I'm planning. Between sub-optimal shifting or staying at home, I know which one I'm going for.

For what it's worth, the chain has never left the big or small sprocket, but as the top jockey wheel is further from the casette, it sometimes requires a bit of overshifting to nudge it to a bigger sprocket. This makes total sense, and you descibe the reasons in your post better than I would ever be able to.

As for a proper solution, your post helps me with useful information. I'm leaning towards getting a new shifter + derailleurs to use the 32t. Certainly not the most economical option, but it's dawning on me that anything else will be a compromise with less than satisfactory results.

Guess I now need to make up my mind between a Chorus HO or an eTap upgrade

by Weenie


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