Can someone explain brake fading?

[mbogosia]

I replaced my rear pads and bled the system and replaced with ATE fluid. Ever since my brakes squeak and I can feel them kind of pulsing slightly. I noticed my rear rotors looked pretty worn, but why didn't they pulse and squeal before the pad repalcement? I put anti squeak compound on the back of the pads also.

[winfred]

theres a couple forms of fade and both are heat related, the most common is gas plaining, heat vaporizes various compounds in the pad material and this makes a cushion of gas between the pad and rotor that the pad surfs along on (slotted rotors deal with this by giving the gas a place to go), this doesn't severally effect braking performance but it does lengthen stopping distance. the other form of fade is not something that one encounters on the street, basicly you get the brakes so hot the fluid boils making air in the systems depriving you of stopping power, it depends on the condition of the brake fluid on what temp it boils at, older fluid has a higher moisture content and lower boiling point. pulsing usually means a warped rotor or a rotor with a bad spot like bad rust from sitting and the clean spot where the pads were, i stop squeeling of my cars by running them up over 100 mph and doing a hard brake down to about 40 or so, if it's still doing it days later i do it again

[632 Regal]

another possibility is when you replaced the pads the rotors got dirt behind them, pull the rotors, wire wheel behing the seating part of the disks and the axleflanges, coat them with some grease and also clean the mounting surface between the wheel and rotor flange. if you didnt have it before then something changed, maybe you reinstalled the rotors in a different posistion and the built up crap is holding the rotor in an off position.

[mbogosia]

I noticed a hairline crack in my right rear rotor right at the edge. It was barely visible. Besides that the rotor had plenty left on it. I might replace the 2 rear rotors just to get it done and then see how it goes from there. Thanks Winfred.

[632 Regal]

never use used pads on new rotors unless you can have them surfaced, new pads with used rotors is ok. cracked rotor is garbage food