I just got a Gary fisher 04 tarpon aluminum frame, to feel out the sport. I was riding fine on some easy local trails until I came to some parts of the trail that were pretty sandy. Although I did not fall off, my bike was fishtailing alot, giving me a few close calls, where I had to stop altogether. Any advice to help? I could be that I upgraded ffrom my old bike (ParkPre grandsport 94 Chromo). It was a much smaller frame,16" vs 19.5".