I went to replace my rear brake pads today and found a white composite shim placed under a stainless plate attached to the old pads. I figured they belonged there so I put them on my new pads and tried to re-install with no luck. There just wasn't enough room with the shims in place. My question to all y'all is, do the composite shims need to be there? As you can understand, I don't want to compromise my stopping power.