It’s only a slight improvement when accelerating. At steady state, the wheel weight is balanced out (half moves backwards, half moves forwards). GCN have done

It’s only a slight improvement when accelerating. At steady state, the wheel weight is balanced out (half moves backwards, half moves forwards). GCN have done some non-scientific experiments on their YouTube channel on this. The biggest benefit to carbon wheels is you can make them deeper for less weight penalty (vs aluminium) which gives you a significant aero benefit.