So this has been happening for a while and it's really bugging me now! I'm guessing my rear passenger side caliper has seized up as the corresponding wheel is showered in a lot more brake dust than the other wheels. When I'm reversing or going backwards down a hill (to park) and I apply the brakes, I hear a really LOUD humming! Not sure if this is caliper related, or could be wheel bearing? Would appreciate any help! Thanks Amjad