I am having a problem with my rear brake ever since I replaced my rear tire. I have drained and refilled the rear brake fluid with Dot4, bled the brakes.

The problem is the pedal goes down and the brake seems like its about half strength. checked the pads still have over 1/8 inch of pad left. tried pumping the brake, doesn't do anything for me. not sure what else to try.

 

I posted a similar problem in the Dyna section. I was advised to clean the pistons. I will do that in a few days when my new Lyndall pads come in. You have to extend the pistons out and clean them, then retract them manually and install pads. Good luck!