Uneven brake pad wear, replaced twice

Mendal is so correct. If your mechanic opened the drivers door during his work, this too can mess things up. If he didn't disconnect the battery, that can mess things up. I have done may brade jobs, and, I will leave the job of getting my rear brakes done to Hybridpit here in the OC. Make sure your mechanic knows Prius brakes. Keep the drivers door closed. Disconnect the battery. I can tell you having done many a brake job, that I never would have worried about the battery being disconnected or opening the drivers door.

 

I fell victim to this situation - outer rear pad angle heavily skewed - contacting top edge of rotor only. I, too, have done tens of brake jobs in past, but must have screwed this one badly. This was the case on both or my rear brakes recently.

All of the prior post info makes sense - e-brake engagement attempts to rotate piston - if it rotates when there is excess gap, piston can rotate beyond the orientation intended to occlude the pin, and therefore fails to make flush, right-angle contact with the pad.

My learning from applying Mendel's meticulous process spelled out earlier in this thread:

avoid any e-brake engagement until excess gap between piston and pads has been fully removed by 2 rounds of pedal pumping

-1) pumping pedal with battery disconnected (so rear electric pump remains inactive)

in my case this closed the gap somewhat, but failed to fully lock up the rotor

-2) pumping pedal with battery connected to further close the gap

this caused my rotors to lock fully

I guess because it's a regenerative system, when you press the pedal (with battery connected) - the "system" chooses whether or not to actually send pressure to rear calipers. If it does send pressure, that must be done by electric pump instead of from actual master cylinder on pedal.

e-brake system uses some sort of mechanical (non-hydraulic) threaded design to engage the piston when e-brake pedal is depressed - which will induce rotation of the piston if the pin is not engaged properly to prevent such rotation of the piston.