by George Lyle and Michael Benthin
"None of the rebuilders bother aligning the
pistons, and or replacing the retaining plates.
I don't know what the retaining plates do."
George Lyle writes:
What they do, for all I know, is allow one end of the pad to contact the disc just a bit before the other, allowing smooth engagement and reducing noise. You'll notice that the retaining plates are mirror images of each other, and shouldn't be swapped left-to-right.
"The Bentley shows a special tool for orienting the pistons"
I used a small set of channel-locks inside the piston. You can pull the handle apart and wedge the head of the tool inside the hollow of the piston, then turn the piston. Actually, it turned pretty easily, so you could probably just push it around with a screwdriver on the "step" of the piston.
Michael Benthin writes:
Yes, I've noticed that the cutout on the piston is designed to apply force unequally to cause "toe-in" on the pads just like on bicycle brake pads! I presume the backing plates are to keep the alignment of this piston uneqality, or they could rotate out of position! If I find the plate "flattened" I punch out the tabs so they can hold the piston.