I have had a knocking sound when I start, stop, or go slow. The tires, brakes, and rotors are OK. I had no movement at all on the passenger side when I removed that one. When I got to removing the drivers side tire, I could still turn the rotor about an inch forward or back while in park and the other tire on the ground. It turns the entire shaft. I don't think this is normal. What is happening and what needs to be replaced, fixed, or tightened?
Thanks,

Most european cars like VW, Audi, Porsche, Saab, MB, BMW, have composite brake rotors. This type of rotor can NOT be turned and must be replaced every time pads are changed. Turning composite rotors damages the material causing a BIG hazard to the driver.