Trying to clear up what I mean - as I pedal (on bike or in the stand) the chain as it goes over the lower pulley will actually come out of alignment with its teeth. The pulleys teeth don't in between the chain rollers but rather jump up and ride on the sledge of the chain and then it'll fall back in.I'm not exactly sure what you mean but given that I'd check for hanger alignment, bent cage, freely rotating pulley and worn pulley teeth.
No, I put it all back together now. But no teeth stood out from the rest in terms of them being jacked. They were all wore the same.Do you have a picture of the teeth on the lower pulley?
I have seen that when the teeth on a nylon lower pulley get jacked up due the RD getting bent or the alignment being off depending on the cassette.
Ahh I did mess around with the front ring the other day. Yes it rally only happens on the largest cog. Also an older 135 rear spacing on the suspect vehicle.Does this happen all over the cassette or more towards one extreme? I've had this sort of happen in the biggest cog on extreme chainlines where the front ring is pulling at such an angle that it is too much for the chain to stay on properly in that ring - middle ring, not outer, just on a 135 hub.