Endless belts, such as for use with e-bikes and other personal mobility systems such as standard bicycles, wheelchairs, scooters including electric scooters, and other systems that utilize a belt for transmitting power to impart motion to the system. The belts are particularly suited for inhibiting “tooth jumping” during use, having a curvature coefficient of no more than 0.01%, and in some embodiments less than 0.005%, with a compressibility coefficient of no more than 0.00075. The belts can utilize reinforcing cords, such as carbon cords, which when incorporated into the final belt, some cords have an open porosity of 10 vol-% or less, in some embodiments 5 vol-% or less.