brake pad backing plates

[Flieger]

I have always been told that backing plates reduce the noise of brake pads by reducing vibration between the piston and pad caused by the pad vibrating next to the rotor.

I never understood how a plain, flat piece of metal could do this. Is there a spring pressure effect when the piston shoulder cutouts are taken into account? Does the "knock-back" pin mechanism in the Ate calipers have an effect that promotes vibration?

My Ate brake pads had backing plates on the old S caliper pads. The rear M's had Textar pads with the plates bonded to the pads. The new Ate pads did not include backing plates and the Textars were again bonded to the pad.

How do backing plates work?

[hcoles]

almost anything put between the pad plate and piston will alter the compliance enough to change or reduce noise... it also cuts heat transfer to the piston, also a good thing.
A pad plate can also alter how the brakes feel through the brake pedal, but I don't recall someone mentioning this as an issue.

More detail on why - the back of the pad plate is not prefectly flat so when you put a layer of metal over the surface you create a spring of sorts against the piston.

That's my theory anyway.