Loose axle nuts will let the rotor walk back and forth and move your pads out just enough to give grief.Same with wo out bearing housings and inner ball bearrings. Same with slightly bent stub axles and warped rotors.Trash and dirt between rotor and hub. I have put feeler gauge blades between the roller bearings and the housing to take up "Up and Down slack". Frozen rusty calipers won't bleed out from my experience. Just my 2cents.