The trail I follow up the mountain near my house is fairly uneven and it has crossed my mind that it might be too rough for my bike. Both times i've gotten it trued it only lasted maybe 4 or 5 rides, but the shop I take it is reliable.

There is a very subtle grinding noise that's also accompanied by an almost, hollow noise?(that probably doesn't make much sense). It gradually slows down, but when it does it moves faster and slower at different places. It seemed to be stable when I wobbled it.

Thanks for the all help and I apologize for the vague descriptions.