I had to replace the disk, not long after I bought it, less than 50 miles, loaned to employees for a long weekend at Jericho Park, first, the rear skid pan got ripped off, then as I'm told, one of em was doing cookies in rocky terrain, threw a stone right into the disk, and bent it. They removed the rear caliper to get out.
NEVER AGAIN will I loan my 450i, I let my son drive while I ride, that is about it
FWIW, you can't loosen up the rear end enough to slide the disk off the end of the shaft, ya gotta unhook it completely
YES, it holds up well, I've driven a mile wondering why it didn't seem to have power only to discover I had the parking brake on......doh!, that was a long time ago, nearly 2000 miles, brake still functions perfectly, and parking brake still holds on the steepest hills (I haven't tried it on anything over 25%)
did I say I beat the crap out of mine