No heat, bad for the seals abd bearings. The sledge trick works well, but can damage the rim if you get carried away. I use a 6' prybar at work to pop off stubborn wheels, usually don't even need any penetrant. When you get it off, put a light coating of anti-seize on the hub, where the wheel seats and on the center hole of the wheel. Just a light coat, doesn't need to be much. That will prevent seizing in the future.
