The spindle did not slip back, it just kept needing to be moved till there was no adjustment left. Some of this undoubtably accounted for by loss of metal on the rear pulley but mostly and there can be no other answer, this is down to belt stretch. Maybe I should just wear a lighter boot on my right foot?
I would have liked to have videoed the belt while driving, to see if it tracked differently under differing load conditions. We can, after all, only adjust the tracking while the vehicle is stationary. My experience of belt conveyors makes me think that the tracking would be all over the place as the load changed. Different animals I know but I often heard the belt squeaking against the side plates but not consistently, which made me think that it moved as the load changed. For a while I used to try to track the belt to eliminate side contact and squeaking at all times but sadly life is too short.
