Fnaar said:
(Shimano Sora on road bike)
Hi folks
On rear derailleur, the jockey wheel appears to be rubbing against the sprocket when in lowest gear: have adjusted B-tension screw, but even when it's fully in, there's still rubbing... any ideas oh fountains of knowledge?
All other gears and changing no problems whatsoever.
The B-tension screw adjusts the angle of the body of the derailleur in relation to the sprockets.
This is most critical when you are in the lowest gear on the rear cluster (ie the largest sprocket).
If the chain is too long then the angle of the derailleur's jockey arm is at a more acute angle forcing the jockey pulley upwards towards the sprocket.
The reason that it has got more noticeable is most likely that the chain has worn and therefore lengthened further.
If your derailleur or hanger were bent, you'd almost certainly either a) have difficulty with all gear changes and
possible have the lower end of the jockey arm (the tension pulley) bent towards the spokes.
When you're on the middle chainring and the middle sprocket at the rear your jockey arm should not be more than about 45 degree to the vertical. If it more horizontal than that, your chain may be too long.
Check the angle of the jockey arm for the chain on the middle chainring and the largest sprocket - the jockey arm should be near vertical.
Cheers