I'm replacing pads on my TRP Hy-Rd brakes. These are cable actuated hydraulics. Using tire levers, wrenches, etc. I have not been able to push the two pistons far enough apart to fit the rotor between the pads. I can move one piston, but the other follows, so there's no increase in the gap. I've tried pushing the pistons apart both with and without the old pads in place. Not having any luck. Any suggestions?