I have had my rear derailer sucked into the spokes on my giant ac while riding hard on fast rough single track. Three times. Busted spokes, derailleurs, hangers and chains!!! This bike works great until the drive train self destructs in an instant. The lbs says that there is no reason other than a stick or rock hit the derailleur and pushed it into the rear wheel. I think it is severe flex in the rear wheel and triangle. Anybody got any ideas on what causes this and any possable cures??