Rear Brake Lose Power After Brake Pads Change

Sounds to me you somehow got air in the brake line.

 

I would suggest making sure no grease got on the brake disc or pads.
Give the disks and new pads a clean with brake cleaner, and maybe roughen the surface of the pads with sandpaper to get rid of any manufacturing glazing
Also try bleeding the brakes should any air have got in the hoses/calipers

Good luck

 

If the pedal firms up after a few presses you have got some air in the system and it needs bleeding.

If that's not the case bear in mind new pads need a few miles to bed in before maximum efficiency.

If it's more than that you may have disturbed some crap around the pistons while changing the pads. Did you expose the pistons a little and clean them up during the pad change ? If not, sounds like you need to have another look at the caliper. Have a clean up inside with some brake cleaner and an old toothbrush.

There's bound to be a YouTube video on how to service a caliper if you need it.

 

It's normal as pads bed in. Give them a few Mike's with hard use but not overheating them and see if they come back. Having checked of course that you out did the change correctly

 

If you’ve only changed pads, you won’t have any air in the system.
Recheck your pads are located correctly and not getting caught, as this sounds like the pads are not returning correctly so more pumps are required to get the pedal back