I’ve never heard of “carriers“ in a braking system. Are you sure youve not mis-heard the word “callipers”?its the part of the brake that squeezes the pads against the discs. BMW believe that they need changing as im assuming they stick when reversing.
anyway, i had discs and 4 sets of pads for the noise. nothing.
carriers changed and all good so far.
The calliper holds the pads, and the hydraulics that push and retract the pistons that push the pads against the discs.