# 2015 Chorus Rear Der. B screw



## thosj (Mar 24, 2010)

OK, 2015 Chorus rear mech in hand. It seems to have both the traditional Camp screw (rack and pinion) at the lower pivot and a "B" screw at the mount pivot. No mention in the docs included in the box or online. So do we now have a "B" screw on a Camp rear mech? Do they both contribute to the same adjustment, the 5 to 7mm upper jockey wheel distance from the big cog? I assume Record and SR have the same?


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## aa.mclaren (Jun 25, 2008)

The new parallelogram design for 2015 Campagnolo rear derailleurs places the upper jockey wheel a lot closer to the cassette cogs across the shifting range. I am guessing here, but it might have been necessary to have this b-screw for certain derailleur hanger/drop out designs as with frames having rearward facing drop outs. It could be the new parallelogram gets the chain a bit too close and tight otherwise. If your frame has a conventionally sized hanger on vertical drop outs it may be that you don't have to touch it... but please do let us know how that works out!


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## bikerjulio (Jan 19, 2010)

No mention in the instructions, which only mention the conventional "H" screw although it's now a "G" screw. Are there no limit screws? Instructions 5.3 say it's specialized Campy mechanic only. I'm having trouble understanding how that works in practice.

http://www.campagnolo.com/media/files/035_265_User_manual_rear%20derailleur_11-speed_Campagnolo_Rev01_08_14.pdf


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## thosj (Mar 24, 2010)

There ARE limit screws. They are now socket head set screws, pretty small ones and look like they'll end up pretty much down flush with the surface. I suppose they LOOK small because they have no heads, thread is maybe the same, I haven't checked. Not mounted on a frame yet, awaiting a paint job. 

I find the docs painfully inadequate!! i have NOT tried scanning those QR codes, but what are THEY going to do other than take us to some web page?

I have a couple pics, but I've never attached a pic here and I'm not currently on any sharing sites. If they show up, one shows the limit screws, one screwed back out a long way, the other flush. Bottom photo, left side, near cable adjuster. Also shows the said "B" screw!!


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## bikerjulio (Jan 19, 2010)

Campy instructions are not that bad in comparison to others. (Check out a SRAM instruction sheet!) Historically they have often had translation problems.

There is usually a lot more detail in the Technical Manual, which is available to download.


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## thosj (Mar 24, 2010)

The "rack and pinion" screw, on all rear mechs I have, are the phillips with one slotted across for flat blade screwdriver, too!! i guess they figure once adjusted, you won't be messing with those much.

That said, in my opinion, Chorus is the new Centaur. I have never laid eyes on a new Record or SR rear mech, but this one is molded composite of some type with obvious mold lines all over it!! No big deal, likely, and this thing is light (feeling, anyhow), but somewhat cheesy looking with the mold lines!!! All black, 'tho, so not obvious from 4 feet away!!


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## bikerjulio (Jan 19, 2010)

Found this picture. The bodies look to be the same across the range. Hard to tell 100% though.


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## tka (Jun 11, 2014)

The tech manual doesn’t give any additional information on adjusting the “B” screw. At least the version I have, which now looks like it has been taken down, didn’t even mention it. Be careful adjusting it – it is aluminum and either they use a very tight thread fit or the screw in mine was corroded (or both) (and it didn’t look like any typical threadlocker) but it is very hard to turn the screw if there is tension on the derailleur. Use a good Phillips screwdriver, and rotate the derailleur away from the stop before trying to adjust it. Don’t ask how I found out…and I was just playing with it to see how the adjustment worked, my setup was fine with the screw fully out. And yes, it does appear to be an additional adjustment for the 5-7mm spacing (CW increases the spacing) although I suspect it is for setting minimum clearance on the cogs. The new design gets the cage pretty close if there is more than a couple tooth difference between cogs.



thosj said:


> That said, in my opinion, Chorus is the new Centaur. I have never laid eyes on a new Record or SR rear mech, but this one is molded composite of some type with obvious mold lines all over it!! No big deal, likely, and this thing is light (feeling, anyhow), but somewhat cheesy looking with the mold lines!!! All black, 'tho, so not obvious from 4 feet away!!


The knuckles on SR/R/C are the same molded technopolymer part on all of them. Or at least on the R & C units I’ve seen (haven’t seen a SR yet.) Other pieces of the derailleur change between the groups but the knuckles all appear the same. I agree, it does look a little cheese but it isn’t noticeable from a normal viewing distance.


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## bikerjulio (Jan 19, 2010)

@tka, so are you saying that it's possible to run out of adjustment with the "G" screw, and then need to resort to the "B" screw? What cassette are we talking about?


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## thosj (Mar 24, 2010)

Almost HAS to be, doesn't it? What else is it for other than, perhaps like mentioned, to accomodate different dropout stop locations a bit.

I still say Chorus was too good to be true for the last 15 years, but I think they're on to us!!! Say with me, Chorus is the new Centaur. Nice stuff, and it IS cheaper than before, it seems, but still........ I paid US$1009 for the group, from Ribble to US, which seemed cheap, but I've not bought a group for years. Piece parted before, but can't do that yet for 2015, and it's getting harder to do that overall. I needed to build yet ANOTHER bike and wanted to try the new stuff for fun.


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## bikerjulio (Jan 19, 2010)

When you think that Campy RD's have managed without a "B" screw for at least 15 years, that the clearance requirement hasn't changed for 2015, and that the old RD's will go up to a 30T sprocket at least, it raises the question why they need it now all of a sudden. And to add to the mystery, fail to mention it in the instructions.


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## tka (Jun 11, 2014)

bikerjulio said:


> @tka, so are you saying that it's possible to run out of adjustment with the "G" screw, and then need to resort to the "B" screw? What cassette are we talking about?


On my setup, a 12-25, it worked just fine with the screw all the way out. But playing with the setup it appears that if you were to run a 1X-29 you might need tighten the "B" screw to get the pulley wheel to clear the 29 cog, particularly if the hanger length is on the short end of the tolerance. IOW it looks like it works the same as a Shimano "B" adjustment, but since it changes the derailleur body angle and thus the upper and lower pivot tension it affects the "G" adjustment as well. But I don't think that is its primary purpose.


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## tka (Jun 11, 2014)

bikerjulio said:


> When you think that Campy RD's have managed without a "B" screw for at least 15 years, that the clearance requirement hasn't changed for 2015, and that the old RD's will go up to a 30T sprocket at least, it raises the question why they need it now all of a sudden. And to add to the mystery, fail to mention it in the instructions.


What I think changed is the lower pivot is now higher than it was before. The higher pivot point makes it easier to keep the clearance to the cassette but increases the likelihood of the pulleys being too close to the cassette necessitating the additional adjustment. Not mentioning it in the instructions is just sloppy.


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## tom_h (May 6, 2008)

Started installing a 2015 Chorus groupset. 
The so-called B screw , as-received, is mostly unscrewed out.
I tried turning the B screw , with no chain or tension on the derailleur, just as a check.
The screw is locked in extremely tight, and the screwdriver was starting to round off the screw head slots -- so I stopped. Hopefully no adjustment is needed on that screw. 
Using such a soft screw material, instead of steel or Ti, is lame.


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## thosj (Mar 24, 2010)

I didn't even try turning mine. I got it adjusted the old fashioned way and it works flawlessly!!


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## tka (Jun 11, 2014)

tom_h said:


> Started installing a 2015 Chorus groupset.
> The so-called B screw , as-received, is mostly unscrewed out.
> I tried turning the B screw , with no chain or tension on the derailleur, just as a check.
> The screw is locked in extremely tight, and the screwdriver was starting to round off the screw head slots -- so I stopped. Hopefully no adjustment is needed on that screw.
> Using such a soft screw material, instead of steel or Ti, is lame.


Exact same thing happened on mine. It looks like Campagnolo used threadlocker on the screw. I replace my screw with an aluminum M4x10mm socket head that I happened to have laying around. Even with the socket head the screw turns very stiffly just before it pops out the other end. FWIW you can get a replacement screw, it is part of Campagnolo kit RD-SR005.

View attachment 305829


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