# Campy B Screw?



## boleiro (Jun 11, 2010)

Trying to set up a Centaur 10 Speed Derailleur. Not sure of the year, its the one in the pic. I've got it dialed in nicely except for the two lowest gears. Getting a rattling noise, and I'm pretty sure its the upper pulley rubbing the chainc/cassette. I know I should adjust the b screw to lower the pulley away from the cassette. But, I can't seem to get it to move. I'm tightening and loosening what I to be the b screw and i see absolutely no movement. 

the directions on campy manual is useless and the parktool instructions aren't campy specific. 

Any guidance is welcomed.


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## danl1 (Jul 23, 2005)

I know you mentioned that the manual is worthless, and it doesn't say alot, but just for the sake of reference,

http://www.campagnolo.com/repository/documenti/en/10s_Rear_derailleur.pdf

Page 25.

Obviously, Campag doesn't use the B-screw in the same way that Shimano and SRAM do. IMO, that makes them slightly more sensitive to proper chain length - and set up as Campag recommends. So that's another place to look. 

Also bear in mind that this is a spring-tension adjustment, so it won't make a hard movement like a limit screw does. Adjust, pedal and shift a bit to see how it acts, repeat.

Good Luck!


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## C-40 (Feb 4, 2004)

The Campy screw performs the same function as any other B screw. If the screw is turned counter clockwise (loosened) enough, it will disengage and do nothing further. Fully loosened, you get the maximum clearance between the largest cog and upper pulley.

The chain length is not set any different with Campy. With current 11 speed RD, there is one chain length that produces the maximum wrap capacity and will work with any Campy 11 cassette.


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## danl1 (Jul 23, 2005)

C-40 said:


> The Campy screw performs the same function as any other B screw. If the screw is turned counter clockwise (loosened) enough, it will disengage and do nothing further. Fully loosened, you get the maximum clearance between the largest cog and upper pulley.
> 
> The chain length is not set any different with Campy. With current 11 speed RD, there is one chain length that produces the maximum wrap capacity and will work with any Campy 11 cassette.


The screw performs the same function, true. But it does it differently. On Shimano, you are balancing the pivot spring against a comparatively weak cage tension spring. On SRAM, the B functions a bit more like a limit screw. On campag, the cage spring does it all. 

And you are right, that Campag has one 'right' method. But there are other methods. Using a minimum-length method can means that the relative tension on the cage spring has to be quite a bit higher (vs. a campag-spec'd chain length) to pivot the der. body. 
Taken to extreme, it can challenge the spring to do it well. I'm not sure if it's in the current versions, but this used to be mentioned in the troubleshooting section of Campag's tech docs.


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