sekaijin

Checking back in with C&V after a long hiatus ... I feel a little guilty, but I know this is a forgiving group!

Problem: I ride a road bike with a Campy 8spd rear derailleur. I believe the RD is Chorus, circa 2000:




The problem is, the RD no longer tensions the chain enough. The chain tension is slack enough that the chain slaps the top of the chainstay when I coast.

I gather this could be an issue with one or both of the springs on the hanger bolt or the cage return bolt.

Those springs are RD-SR008 and RD-SR109 in this diagram (not the same Campy RD).

On my RD, both springs still have tension - so they're not outright broken. But maybe losing tension over time?

Anyone have experience with this issue - would replacing one or both of those springs fix it?

Thank you!

alcjphil

Excess friction in the freehub can cause the chain to sag when you coast which would result in the condition you describe. I would check wheel and freehub bearings before looking at the derailleur as the problem

Dave Mayer

Agree with the freehub recommendation. If there is too much friction in the freehub, then the chain will bunch up during coasting. Sounds like it is time for you to pull apart your hub/freehub for annual service. More often if you ride in the rain.

Also time to pull apart this derailleur. The springs do not weaken, but eventually all derailleurs get filled with road grime, and the grease dries out and stiffens up. For someone experienced, this is a 30 minute job - to disassemble the derailleur down to the springs and pivots, clean and regrease and reassemble. Good as new, unless the pivots are worn out. Fortunately this generation of Campy derailleur is easy to service, relatively speaking.

You are going to do this yourself, as in no bike shop will have the time, experience or motivation to do this. If you leave it in shop hands, they will carelessly slap on a replacement Shimano rear derailleur (Altus: yuck) and then the shop and then you will spend countless hours trying to figure out why the indexing is way off. BTW: a new Campagnolo derailleur, as in anything made after the year 2000 will not index correctly with your generation of parts.

sekaijin

Thank you alcjphil and Dave Mayer , sounds like a plan.

I've rebuilt this freehub before (annual service? 🤣🤣🤣 it was 11 years ago) so that should come back to me. I should even have the Campy freehub tool in the back of a shop drawer.

As for taking apart and rebuilding the derailleur - that'll be a new one for me. How hard is it? Any instructions out there?

Dave Mayer

Not too hard; easier than refurbishing Ergopower shifters. The hardest part is getting the C-clip back on the upper pivot bolt, while both compressing and pre-loading the spring. An L-shaped 3mm hex key helps here.
On your derailleur, servicing the lower bolt and spring should be self-evident.

oneclick 

Clamp the hex key vertically in a vice, just enough projecting to hold the pivot bolt. It'll stay put and you have only two things to deal with.

Kabuki12

When I had that problem it was my freewheel . As soon as it was lubed correctly the tension in the Campy NR derailleur did its job. I have 50 year old Campy mechanisms that still have great tension .

mpetry912 

I am in agreement with the freehub / freewheel gummed up.

a good opportunity to spray your aerosol lube of choice into the nooks and crannies and see if that improves the situation or indicates how to proceed

/markp