I have purchased a MTB a month ago and recently I started hearing this strange noise when riding. It comes from the rear wheel and when I apply the brakes slightly the noise stops. It comes on and off with the wheel rotation (as if something is stuck to the wheel somewhere) and sounds like a scratching noise.. The problem is that once I get off the bike, the noise stops. I have got Shimano Deore Hydraulic Disk Brakes (BR-M525). I removed the brake pads, cleaned them and re-aligned them but no to avail. In addition, after riding for an hour or so, the noise becomes really loud, like something is being badly scratched. But yet again it disappears once I get off the bike. Anyone have a clue what this could be. Its driving me crazy and I do not want to be doing further damage somewhere else by riding it further.