I've got some avid Juicy's and this never happened

[onebigpssy]

but the last two pad replacements on the back end - one pad keeps falling out - has anyone else had this problem? Very weird.

[halfnhalf]

do the backing plates on the pads have a hole stamped into the metal? There is a small nub on the piston that engages into that stamped hole to hold the pad. In addition, there is also the retaining clip that snaps over the four tabs once the pad are installed in the caliper.

[jetboy23]

Like halfnhalf said, there should be a nub in the center of the piston that holds it in place along with the magnet. Check if that is broken off. Also, when installing them, are you getting the "click". Some brands other than Avid seem to be a tighter fit and require a bit more force to get them fully seated.

[bsparacino]

I had the mysterious pad falling out of my rear ultimate until I realized that nub was corroded so badly it was not engaging with the pad.