Campagnolo 11 speed: don't use "b" screw

Discussion in 'Cycling Equipment' started by BobNYC, Dec 9, 2016.

  1. BobNYC

    BobNYC New Member

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    Many of you may already know this, but for the rest of us... The traditional way to adjust clearance between the top rear derailleur jockey wheel and the cassette is to adjust the "b" screw ("body screw"). The proper clearance is critical for crisp shifting. The "b" screw typically goes between the RD body and a tang on the derailleur hangar.
    While Campagnolo still has a "b" screw on their 11 speed RDs, that's not the way to adjust clearance. They don't even reference this "b" screw in their technical manual. Instead, the clearance is adjusted with what Campagnolo calls the "h" screw (no, that's not the derailleur high limit screw).
    The "h" screw is a Phillips head screw on the bottom on the derailleur cage below the top jockey wheel. The procedure is to put the chain on the small chainring and the largest cog, then adjust the "h" screw until you have 5-7mm clearance between the top jockey wheel and the largest cog.
    Don't ask how long I suffered with poor shifting (and cursed Campagnolo!) before I read the tech manual carefully and stopped trying to adjust the "b" screw. Now shifts are crisp and decisive, just like Campagnolo has always been.
     


  2. CAMPYBOB

    CAMPYBOB Well-Known Member

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    Yeah, Chorus refers to it as the 'G' screw.

    Which side of shimaNO's 11-speed long arm front derailleur cable anchor bolt to use with a given frame routing bit me in the ass for a few weeks until Old Bob Cat set me straight here on the forum.
     
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  3. CAMPYBOB

    CAMPYBOB Well-Known Member

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    I had to look...neither my Chorus 11-speed and 10-speed derailleurs have the traditionally located (on the derailleur hanger pivot joint) 'B' screws. They only have the screw located on the pulley cage pivot joint. My 10 speed derailleurs are 2006 and 2007 models and my 11-speed variants date as late as 2013 or 2014.

    So no 'B' screw...no wonder the tech docs do not mention them and yet as I read through a Chorus User Manual on the Campagnolo website the drawing of the derailleur on the setup page clearly showed what might have been a 'B' screw! And some older threads on other cycling forums have guys saying they need advice as to which of the two screws to turn.

    What year and model Campy derailleur do you have that has both screws?

    This 2016 Chorus tech doc http://www.campagnolo.com/media/fil... rear derailleur - Campagnolo_Rev02_04_16.pdf clearly shows and references screw 'L' as a 'B' type adjustment used to control chain slack! See page 6, Fig. 10.

    It also calls the cage screw out as the 'H' screw.


    This is the 2015 User Manual for Chorus and it is the one calling out the 'G' screw on the pulley cage. It also, as you alluded to, makes no mention of an 'l' screw ('B' screw). But, go to page 35 of the pdf file and blow up the picture...it has what looks to be an 'l' ('B') screw!

    Go figure!

    Campy must have dropped the 'l' screw or introduced it later?
     
  4. gfkvelo

    gfkvelo New Member

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    The required information for correct adjustment of the derailleur on an in-spec rear hanger is in the technical documentation, you just have to read the documentation, or in the absence of the paperwork, understand what the screws are actually doing ...

    Campagnolo derailleurs, after the initial introduction of the sprung-drop-parallelogram design and up to 2001, either had a B screw, or some other piece of hardware that did essentially the same job by a different method (Athena 8s used a small, toothed "wedge" introduced into the back of the B pivot housing before assembly of the dearilleur to the hanger, for instance).

    Prior to that, designs were such that either it would have served no purpose, because there was no springing in the upper pivot housing.

    In any RD, Campag, Shimano, SRAM, Suntour, where there is a spring in the upper pivot housing, the B or H.screws are actually doing exactly the same thing, from either end of the parallelogram.

    The screws are driving the anchorage of a coiled spring in the direction of spring tension increase - so as the B screw is screwed in, it's increasing the tension on the upper pivot spring. If the upper pivot springing is increased, relative to the lower pivot springing, the derailleur pivots around the top pivot bolt "backwards". That moves the derailleur away from the cassette so opening up the sprocket-to-jockey clearance. It's not acting as a "stop" (as many people think), and that is evidenced by the fact that you can still push the RD forwards and bring the jockey into contact with the cassette. The H screw is doing the same thing, leaving the B pivot spring tension the same and simply increasing (or decreasing) the tension on the lower pivot spring to over-ride (or not) the B pivot spring.

    On Campag derailleur designs introduced in 2015 (New CH, RE and SR and in 2017, Potenza), the screw introduced at the "B" point is there to compensate for out-of-spec derailleur hanger designs which misplace the stop that the B-spring normally acts against, which some frame manufacturers are now using. Some of these hanger designs need higher levels of overall spring tension (especially in cases of comparatively wide-range cassettes) and some need additional adjustment to be available - the reason that the use of the "New B Screw" screw is not discussed in the consumer documentation is because it is to be hoped that bicycles will be assembled by technicians who know what they are doing and will check things like hanger spec against the tech docs before they start, and will know how o make such adjustments as are required by the hanger.

    The mistake made is to crash in there and assemble the system without reading the tech docs.
     
  5. BobNYC

    BobNYC New Member

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  6. BobNYC

    BobNYC New Member

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    My Chorus RD is fairly new - purchased in 2015. It has both screws. I've been riding Campagnolo since late 60s, when Nuovo Record really was "nuovo". I "thought" I knew how to set up the gears...I guess I learned (again!) to read the instructions.
     
  7. CAMPYBOB

    CAMPYBOB Well-Known Member

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    My first Nuovo Record was 1973 and I had Zeus and Triplex Sport Campy clones before that. I guess we are both old as dirt and still learning how to deal with The level of teshnical detail required in the 'modern era'! LOL!

    I looked at my pair of Wilier's with Chorus derailleurs and 11-25 cassettes. The gap from jockey pulley to the 25 gear has got to be at least 6 MM (1/4") minimum. I tried to shrink the gap, but both 'G' screws were already full tight. That's as close as it gets with that factory hanger.
     
  8. swampy1970

    swampy1970 Well-Known Member

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    SpankyBob,

    Didn't you know that you just need to reroute the cable, use some Mavic ZAP! shifters and epoxy the rear mech to the frame leaving the required 1mm airgap?
     
  9. CAMPYBOB

    CAMPYBOB Well-Known Member

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    Zap? I've stepped up to the Mektronic 2nd gen crap! Waterproof? Who needs it?! Besides, I'm still trying to figure out shitmaNO front deraileur setup. Backwards or everything this side of a top-pull C-X rig.
     
  10. swampy1970

    swampy1970 Well-Known Member

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    The only thing backwards in that setup is you!

    RTFM - and make sure you get the little 2mm bolt on the wang-dong set correctly.
     
  11. CAMPYBOB

    CAMPYBOB Well-Known Member

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    Yeah, I set it up 'tail in' and rotated it into plane with the chainring using the wang dong screw. The frame already had a stiffener pad for it to bear against. I'm not going to adjust it further until my K-Edge chain catcher gets here.

    I'll have to loosen the FD to install the catcher, so back to square one and go from there. Snow moving in tonight so no road riding for a few days anyway. Back to trainer Hell.
     
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