Spray a good penetrating on the hub register also.That can help get them loose.Then antisieze the hub before you put new rotors on.If you smack them where they seat on the front a lot of times they will pop loose.Did a bunch at work.Dont be suprised if the park brake falls apart also.Had the shoes fall off on a lot of them.You did cut the little clips they have from the factory to hold the rotor on I hope.Rocky