Newbie here. Took my Hardrock out today for it's christening. Everything was great. No major malfunctions, no wrecks, nothing on the bike brokedown, awesome ride! Came home, started cleaning it and heard strange noise coming from rear wheel. With the bike upside down, I pedal and let the wheel spin freely, there's a 'grinding' kind of metal on metal sound coming from the rear cluster. I took the wheel off and turned the cluster manually and sure enough the sound is coming from the part that the cluster is connected to that makes the wheel spin freely (sorry not up with bike parts terms yet). Anyone have any ideas what might be wrong here? I'm going to take it to the shop for my post first ride adjustment and definitely mention it to them. I just want to learn ahead of time, what the problem might be for my own education. Thanks.