On my 96 SC400, anytime I back up and apply the brakes, then go forward and apply the brakes, both front brakes make a one-time metallic tap or snap sound. Then they're fine. I suspect the pads are moving in the calipers. The pads have about 40 percent thickness left according to my shop, so I didn't replace them on the shop's advice. It's really just an annoyance since the brakes function fine, but pretty unusual... anyone else had this happen? If so, did new pads/rotors solve the problem?