So was driving my saab. I parked it and after hour i came back to drive away. I reversed and when i tried to move forward i heard a loud metal sound from front driver side wheel. It sounded just like somekinda metal sheet is grinding on asphalt. Looked on bottom nothing loose. I didnt have tools to remove my front wheel but i had somekinda valvoline high pressure lubricant with me. Looked the wheel once again didnt see anything loose. So i just sprayed alot of this lubricant and vrake cleaner on my disc and caliper. After that sound was gone. What it may have been? I doubt that bearing would make so loud sound. Also i didnt get any grinding spund when braking so it cant be brake pad maybe. The sound wasnt continious but random.