After replacing a part of my Campy Chorus 11s rear derailleur to allow for a 12-29 cassette for my upcoming trip to the italian alps I didn´t tighten the lower adjustment screw enough and apparently dropped it on todays ride. See pic below

If I understand it correctly this adjusts the distance between derailleur and cassette, what is the consequence of riding without this part? As previously mentioned I have a lot of riding ahead and would like a trouble free bike.



I can´t find it on Campys spare part sheet either See pic below.

You run the risk of the top pulley wheel physically being in contact with the sprocket on the cassette. Shift up thru the cassette & see if its in contact or not.

Its not a particularly special screw btw, you should be able to replace it with something from a hardware store.

It's a rack and pinion B Screw. Well, you did right screwing it out all the way for a 12-29 cassette - it needs it. But screw it out all the way and it fails to bite and drops out. My point being, you might find it close to home, like at the point where you set off on your ride or wherever you did the work.

Turning this B Screw counter clockwise increases the distance between the upper pulley and largest sprocket.

In my opinion it will carry on working just fine without the screw, but you will of course have a problem if you take off the 12-29 for something smaller when you get back home.

And it's not a normal screw that could easily be replaced. However, I would guess that it is a standard part used for a long period of time now and across a range of rear derailleurs if you pick up a second hand RD.

You cannot order just the screw. you have to buy the complete cage so that's not worth it.

Second, the chorus is good up to the 12-29 so you didn't need to unscrew that bolt all the way.

The mechanics I know barely touch that bolt and it works perfectly with 12-29.

If you need just the bolt I can help you. I can send you one.

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Thanks for your input.

Bad news about replacing the whole cage. But when checking the distance between cogs and pulley it looks good with the 12-29. So hopefully it will work fine for my trip.

It was a stupid misstake loosing it, but since I replaced the toothed part it connects to it had to come out completely during the "operation".

@ferrarista, very kind of you to offer one. Will check with lbs first, then I might get back to you.

I'd say its an m3 not fine pitch screw.. Replace it with a nylon one like a property WW

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project black

It's nothing of the sort. It is a unique rack and pinion screw that engages the teeth of the 5-RD-SR004 adjustment wheel, as shown in above picture. As you screw in or out the 'thread' of the screw engages the teeth of the adjustment wheel moving it clockwise or anti-clockwise.

Ahh my bad i didnt read things properly try your local campy repair outfit and see if they have any spares from rear mech repairs. It's not that hard to destroy a SR rear cage so I'd be surprised if they can't find one for you

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project black