Really i would stick with the single speed, 2 speeds are great for running on road or doing speed runs because you get great top end. But on the track your really dont need it. Like say you go down the straight and then slow down and try to go around a corner and hit a jump, well if its still in second your not gonna be able to accelerate as good anymore. For off roading and track use, i would say stick to single speed, for on road and or speed runs go two speed.