About the middle of summer a strange grinding/vibrating noise could be heard from the rear of the bike. the noise could not be duplicated when on a stand, only there when riding. i was able to narrow it down to the hub because this noise would be present when not pedaling. at slow speeds i cannot hear anything, however once i in the 8th cog, its there and annoying. it gets really bad as i speed up while going downhill. i had the rear hub rebuilt, and the cone on the non-freewheel side was replaced(pits had formed). the noise was gone for a week or two, and today on my ride it was back again. any ideas as to what could be making the noise? Am i wrong in thinking its the hub? should the other cone be replaced?