Some brake calipers and/or spacers will rub on the large *rivets* on the Hope rotors. I had this on a bike with XTR brakes. But had no issues with XT on a different bike. If this happens you can either ditch the rotors or file a mm or two off the adaptor/rear brake mount. I took a mm off my XTR caliper mount point (the rear one only) and it worked fine. Still plenty of meat for the bolt to sit on. Shimano might not like it though!