I replaced my pads a few months ago with ceramic pads, within a couple weeks sometimes when I braked there was a scraping noise from left front wheel like metal on metal or ceramic on metal. Didn't do it every time, then all was good for a couple months. It started again, took it to my trusted mechanic and told him both wheel hubs had been replaced about a year earlier. He checked the torque on them and they(the driver side) were not at spec ( I think 117 lb. ft.) he tightened them and seemed to fix problem. Yesterday the same sound again after driving in city traffic after about an hour of freeway speed. Only did it once the whole 200 mile round trip. Would a sticking caliper cause this noise perhaps? I'm totaled baffled by it.