What role do the two thin backing plates on each pad actually play? Are they strictly for squeak prevention? I can't picture how they would make a difference.
I installed Wearever Gold semi-metallic pads from Advance Auto Parts on my 2007 Impreza Outback Sport this weekend, along with new rotors (old ones were warped - new rotors were cheaper than resurfacing). The new pads had a thin metal backing plate already riveted to the back of the pads. Though the OEM backing plates DO fit on the new pads, and the new pads fit perfectly in place with the OEM clips on the caliper mounting bracket, there simply isn't enough clearance for new rotors + THESE new pads + the backing plates. The pistons were fully compressed, and I was able to force the caliper in place over the pads and rotors (snagging a pinhole into one of the piston seals in the process, which sucks), but of course the brakes are then dragging and I'd probably warp the NEW rotors from heat before the pads had worn down enough. The brake pedal feel was also extremely mushy until an extra pump or two (and it went back to being mushy after moving again) - perhaps because the pistons were being forced out farther than their effective distance?
Either way - I pulled it apart again (I have this down to a 5-minute-per-side science now), pulled off the backing plates, and reassembled - the calipers fit perfectly, the car stops perfectly, and I'm left wondering what role the backing plates really played in anything.
Someone help me figure this out