Abstract: A high-speed inertial energy storage rotor having improved spoke elements which connect a fiber-reinforced composite ring to a central hub. The spokes are tension-balanced by the addition of loading weights to their outer ends. These weights increase the centrifugal loading on the spokes such that their elongation at the operating speed of the rotor matches the dilation of the rotor ring. This minimizes radial loading imposed on the ring by the spokes and resulting shear and flexure stresses in the rotor ring and the spoke-to-ring bond. The spokes are pre-shaped to follow a catenary curve at operating speeds so as to place the spoke in pure tension and avoid undesirable bending moments and flexure stresses which would otherwise result.