My B limit screw seems to have stopped doing it’s job and even at its tightest the centre jockey wheel is pinching the chain against the cassette.
Am I right in thinking that the second motion, turning to the left from the camera perspective, should not be possible?
I’ve compared with my gravel bike, which is a GRX derailleur, but the B screw is a hard stop and won’t allow the movement shown on my road bike above.
I’m leaning towards replacing the whole derailleur, as it’s done over 10k kilometers, but I thought I’d sense check with the community first!
by ValourCat
2 Comments
Reset it to be flush and try again you are over the intended angle
This 105 derailleur and your GRX derailleur are completely different designs, do not use the behavior of one to judge the other. The GRX derailleur is a single-sprung design, with the only spring in the P-knuckle (where the cage attaches). This 105 derailleur (a 5800?) is a double-sprung design, with springs in both the B-knuckle and P-knuckle.
On double-sprung designs, the B-screw doesn’t directly rotate the derailleur body around, it essentially *increases the spring tension* in the B-knuckle. The derailleur is still able to swing forward, it just takes more effort to do so.
If you haven’t changed anything recently (bigger cassette, different chain length, etc) and the derailleur is starting to ride into the cassette when it wasn’t before, the B-knuckle spring may have just worn out. But if you’ve changed your setup recently, maybe it’s an issue with the new setup rather than with the derailleur itself…