Say you want to do a quick and painless brake pad and rotor replacement. The vehicle is on a lift or in your yard on jack stands, the caliper is off, but the rotor is stuck to the hub. Knock-off rotors fit snugly to the wheel hub due to rust, corrosion--and in some cases in which aluminium hubs are used, oxidation. What seemed like a benign brake repair now has you perplexed. Relax; you have some options.
Put on safety glasses.
Spray the centre of the wheel hub that the rotor seats against with a lubricant spray. Be liberal. Use a pick to clean out any of the oxidation or rust if present.
Determine whether you're trying to save the rotor or not. Having to remove a stubborn brake rotor isn't a delicate operation. If you're removing it, chances are you're replacing it. But if you're trying to replace the hub bearing and need to remove the rotor, you're going to have to consider buying a new rotor as well. Otherwise, you could use a torch to heat up the hub area of the rotor and hub and try to knock it off with a large rubber mallet. Be aware that your chances of success with this are slim, though enough heat from the torch may help.
Place the rotor removal tool on a slide hammer. The tool is an L-shaped adaptor that threads onto the end of the slide hammer, and the flat part of the adaptor sits behind the rotor. Strike the slide hammer by positioning the adaptor in several locations. You can use this method to try to save the rotor as well, but chances are you're going to incur some damage and possible warping to the rotor.
Strike the plated fin of the rotor with a 0.907kg. sledgehammer if you're replacing it with a new rotor. Apply more spray lubricant as needed and continue to strike the fin. Turn the rotor every so often and strike it forward and backward until it breaks free of the hub.
Use a combination of the removal steps. In other words, if the rotor is still not moving, use the torch to heat up the hub and then use the 0.907kg. sledgehammer or slide hammer. Determination and brute force will prevail.
Clean the face and edge of the hub with an angled die grinder and sanding disk. The reason the rotor was stuck to begin with is the build-up of rust, corrosion or oxidation from the hub and rotor that fused together. If you don't have pneumatics, clean it with a piece of coarse sand paper. Also, applying a light coat of anti-seize lubricant to the edge of the hub will help for future rotor extractions.