okay, i bought some rotors for my 89 F-250, i tried to remove the old ones, i failed because i could not get the hub off. i took the knob and chrome peice off, but still could not figure out how to get the rotor off. i was told by a friend that there was a tool that did this. i would like to know what the tool is if there is one and how to use it? thanks for any replies.