I replaced the rear brake pads about a week ago, and today I noticed that when I'm reversing, when I apply the brake, I hear a clicking/popping sound. It seems to be loudest when I let off the pedal.

I removed the wheels this afternoon and everything seems tight. What the heck did I do wrong?

http://www.youtube.com/watch?v=KgR-p...ature=youtu.be - Video of the noise. Sorry for poor quality.