I have just upgraded my Cove Hummer to XT 10 speed and when I run the chain on the 11 tooth on the rear the chain seems to rub and try to catch on the 12 tooth on almost every 20 links than run through. It sounds as though the gears are out of adjustment, but they are not.
It does this when you back pedal as well.
It's not the mech positioning (i.e the grub screws that adjust the mech range), and its not the BB alignment either.
I know it not right as it doesnt do this on my road bike which has 10 speed.
Any ideas?
Is the top gear stop screw far enough out?
A little less cable tension perhaps?
What about a bad join in the chain? Are the Shimano 10 speed chains directional and if so is it the right way round?
B Screw? Top jockey wheel may be rubbing on the cassette.
You say it's not the stop screws, but how do you know? It's almost certainly adjustment, either stop screws or the cable tension IMO.
I've had this a couple of times recently on different bikes almost certainly B tension 10spd shadow seems particularly sensitive to the B-tension setting see shimano tech docs for guide on how to set B-tension
Bent hanger?
I had an issue recently that took me ages to find. I had removed the windows on the XT shifters and screwed the little grub screws in and I had put one of them in the hole closest to the levers and it was stopping the ratchet returning fully in the 11 tooth sprocket. It obviously goes in further without the window but I didn't think about that.
Might be worth a try
Thank you all, but the award goes to xanboy, thanks very much once again for your help.