Thanks on the differential fluid changing advice.
The ring I was talking about on the inside of the rotor is apparently an anti-lock brake ring, from what I can tell. Atlantic-British shows it as
http://www.roverparts.com/Parts/FTC1379.cfm
I'm assuming I just remove it to access the rotor to hub nuts and then reattach it once I get the new rotor on the hub.
Tom
