Why isn't my b-limit screw moving my derailleur?
04-25-21, 07:40 PM
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Why isn't my b-limit screw moving my derailleur?
I am trying to reinstall a replacement Campagnolo Mirage rear derailleur. For some reason, when I turn the b-limit screw, it does not move the derailleur at all. I can tighten and loosen the screw, but the angle of the derailleur does not change.
The piece that the screw threads through rotates as the screw is turned, but it does not cause the rest of the derailleur to rotate with it. Sorry, I don't know of a better way to describe this, and my account isn't allowed to upload pics yet. But this is the piece that is held in place with the larger of the c-clips, and is tensioned by the shorter spring.
Strangely, if I remove the chain, so that there is no tension on the RD, it DOES rotate as expected when the screw is turned.
I notice that there is a small gap of about 2mm, between the plastic washer and the metal piece I describe above. If I rotate this (increase spring tension) and press down, I can close that gap. But when I release tension, it slides up again. It's as if the c-clip is too thin, or the bolt too long. Is this normal? Could this be related to the b-limit screw issue in any way?
The piece that the screw threads through rotates as the screw is turned, but it does not cause the rest of the derailleur to rotate with it. Sorry, I don't know of a better way to describe this, and my account isn't allowed to upload pics yet. But this is the piece that is held in place with the larger of the c-clips, and is tensioned by the shorter spring.
Strangely, if I remove the chain, so that there is no tension on the RD, it DOES rotate as expected when the screw is turned.
I notice that there is a small gap of about 2mm, between the plastic washer and the metal piece I describe above. If I rotate this (increase spring tension) and press down, I can close that gap. But when I release tension, it slides up again. It's as if the c-clip is too thin, or the bolt too long. Is this normal? Could this be related to the b-limit screw issue in any way?
04-25-21, 07:47 PM
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The reason to adjust the B screw is to change the gap between the large cog and the der's guide pulley. Have you test shifted the system after adjusting the screw or are you assuming the der will move at the same time as the screw's being turned? Sometimes there's enough friction in the der's cage and B pivots to not move until there's some other forces going on (think stiction). Andy
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