Chorus 12s rear derailleur: cable breaks too often

Back by popular demand, the general all-things Road forum!

Moderator: robbosmans

Post Reply
claus
Posts: 401
Joined: Fri Oct 31, 2008 10:04 pm

by claus

The cable on Chorus 12 speed rear derailleur is breaking between the clamp and the adjustment screw way too often (it does happen about every 4 months!)
AFAICT the "angle" between those two can be very steep and the distance very short thus causing a lot of bending of the cable. If you have this setup: does this also happen for you? How can it be avoided?

The clamp on my 2 derailleurs does not look like the clamp shown in

035_2397_Technical-manual---12s_Mechanical-units-rear-derailleur---Campagnolo_Rev04_06_19_ENG.pdf

(pictures 11 and 12) - maybe that's just a difference between the SR and Chorus derailleurs?

Sorry, I don't have camera to take photos of this, maybe someone can point me to pictures of the Chorus 12 speed rear derailleur showing the same things as those in the PDF?

claus
Posts: 401
Joined: Fri Oct 31, 2008 10:04 pm

by claus

Let's see whether I can attach some pictures after all.
They aren't particularly good, but hopefully better than nothing.
Attachments
Chorus.12.RD.1.jpg
Chorus.12.RD.2.jpg
Chorus.12.RD.3.jpg
Chorus.12.RD.4.jpg
Chorus.12.RD.5.jpg

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



Nickldn
Posts: 1865
Joined: Mon Mar 25, 2019 12:35 am

by Nickldn

Here's a photo of mine, no issues with cable fraying.

Are you using Campy cable (mine is the one with no coating) and is the cable aligned with the groove inside the clamp washer?
Attachments
IMG_20210729_121925.jpg
Giant Propel Advanced SL Red Etap 11s Easton EC90 wheels CeramicSpeed BB Zipp SL70 bars 6.5kg

Vitus ZX1 CRS Campy Chorus 12s Bora WTO 45 disk brake wheels Zipp SL70 bars 7.5kg

SL8 build with Craft CS5060 Wheels in progress

usr
Posts: 888
Joined: Thu Mar 25, 2021 5:58 pm

by usr

Ouch: considering the cost of The Maximum Smoothness it wouldn't take long to amortize even the premium for a Super Record derailleur.

This is not the solution you are looking for, but if there is really nothing better you might want to create a collection of a few rear bend outers in different lengths and start a new inner with an outer generously too long and swap the outer to the next shorter one each time the inner breaks at the clamp. But I'd expect a solution to exist, making this damage mitigation strategy moot.

User avatar
dj97223
Posts: 822
Joined: Sun Nov 06, 2005 7:27 pm

by dj97223

claus wrote:
Thu Jul 29, 2021 12:12 pm
Let's see whether I can attach some pictures after all.
They aren't particularly good, but hopefully better than nothing.
It looks like you've installed the cable incorrectly, such that clamp lip is biting into the cable?
Last edited by dj97223 on Thu Jul 29, 2021 9:26 pm, edited 1 time in total.
“If you save your breath I feel a man like you can manage it. And if you don't manage it, you'll die. Only slowly, very slowly, old friend.”

jih
Posts: 596
Joined: Fri Jan 29, 2016 12:54 pm

by jih

In 20 years of riding bikes, mostly Campag, I've never seen this particular failure. Is it possible that the anchor bolt is being over-tightened? It doesn't need to be all that tight. About 4nm is enough.

Butcher
Shop Owner
Posts: 1924
Joined: Sun Jan 03, 2010 4:58 am

by Butcher

Looking at the cable crush, it certainly looks like it's torqued way too much. You just need to have enough torque to keep the cable from slipping. Anything more does not help. Too much and you'll stress the cable.

https://www.campagnolo.com/US/en/Suppor ... _groupsets

5 min mark

claus
Posts: 401
Joined: Fri Oct 31, 2008 10:04 pm

by claus

jih wrote:
Thu Jul 29, 2021 1:24 pm
In 20 years of riding bikes, mostly Campag, I've never seen this particular failure. Is it possible that the anchor bolt is being over-tightened? It doesn't need to be all that tight. About 4nm is enough.
I'm using Campagnolo longer than that -- and for me this problem only happened with the Chorus 12 speed rear derailleur -- I never had it happen with any of the earlier versions (11, 10, 9, ... speed)

AFAICT it's not over-tightened - I used a 5Nm Torque key and it didn't trigger;
it might look this way in the pictures because the cable is now frayed.

BTW: it seems the pictures are "upside down", sorry about that.
You have to rotate them so the "FG" is shown in the correct way.

jih
Posts: 596
Joined: Fri Jan 29, 2016 12:54 pm

by jih

If it is not overtorqued, it's tricky to know what's causing this. Did you check the clamp for a sharp edge or a burr etc on the clamping edge? Could be a manufacturing error, although seems a bit unlikely it'd kill cables so quickly. I'd be tempted to very gently and slightly file the corner that's cutting onto the cable.

I might also try to find a well calibrated torque wrench just to confirm it isn't over-torqued.

All the 12s mechs have the same geometry so if this was an issue with chorus 12, it'd probably not be unique to chorus; it'd happen in record and SR too.

welchy
Posts: 458
Joined: Wed Jul 01, 2015 4:04 pm

by welchy

I've got some maximum smoothness cable for sale which may help.. I bought 25metres!! So got a wee bit surplus.

FYI never had that issue on my record setup.

claus
Posts: 401
Joined: Fri Oct 31, 2008 10:04 pm

by claus

Could the problem be caused by not tightening the bolt enough?
I took the bolt off and the derailleur body showed lots of scratches there:
this might have been caused by the cable moving "sideways" when shifting?
-- which in turn would cause it to break early.

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



Post Reply