Well son of a bitch, I was cursing General Motors all morning. An easy brake job (shouldn'ta taken me more than 20 minutes) turned into 2 hours.
Usually, I pull the caliper bolts, compress the piston with a small prybar, pop the caliper, pads, and the mount, get out the big brass hammer and give the rotor a whack, pop it off and then reverse the procedure with new parts. About the time I gave the rotor a whack, I knew it wouldn't be easy. I could swear I heard the damn thing laughing at me. I hit it again, and again, and again, and again ... Got out the torch, heated the fuck out of it and hit it again. The laughing got louder and it still didn't move.
Seems GM has a very close tolerance between the inside of the rotor and the wheel hub (Ford does this too on the Expeditions). In areas where road salt is used (like here on Long Island), the inside surface of the rotor rusts to the hub. No matter what you do, you ain't breaking it loose ... until you break out the Sawz-all.
I sliced the rotor down to the hub, squirted everything with penetrating oil, and then beat the fuck out of it some more until it let loose. Hadda do the other side the same way. Notice the rust ring around the outside circumference of the hub, just outside of the wheel lugs.
So, being a guy who looks long-term, before I put the new rotors on I sanded and gave each hub a coating of adhesive copper grease to prevent this problem for the next guy (me or Nunz probably) who services the brakes.
Like I said, this ain't indigenous to GM, just the latest crap I had to do this on. Ford is just as guilty of this poor design and it makes you wonder, after a hundred years of building cars in the United States, how simple engineering fuckups like this still happen. Once again, there's no surprise these guys are on the balls of their ass.