We have not had that problem(knock on wood). I did notice that my bolts the hold the rotor to the hub had become loose. I would say check those every now and then. I also saw you had a topic of rear drum and residual valve for firm pedal. Have you thought about disconnecting the rear brakes period. I know it sounds crazy, but I have them disconnected, they do not get used anyway. I have a pretty firm pedal and don't have to worry about the rear wheel brake leaking as they do. With the Triumph the drums really do nothing, and I felt I would rather have a firm pedal for feel and modulation than the small amount of braking they give. The only thing I can say is my 8 ran quicker this year at IRP and Mid-Ohio than we ever have.