Drum is shearing off from rear bearing spider, probably. Look through the opening at the centre back of the drum. There is a triangle of 3 rivets holding the drum to the bearing assembly. to allow the drum to rotate. There may signs of the metal around this showing fatigue or even shearing off. If its less than 2 years old then contact Crosslee. New drum costs about £80 plus fitting.
John E, October 2010
