While on the stand, I spin my back wheel, hearing a clicking about twice per revolution. Seems to be only when freewheeling. I was thinking maybee hub needs servicing. I dont know much about freewheels, but could this be the cause? And no, it's not the normal clicking heard while freewheeling, it's different and pretty significant. I did do a search, but nothing for while NOT pedaling. Any tips are much appreciated.