A variety of transmission mechanisms are provided that include split pulleys nested within each other in order to reduce the size of the transmissions, to provide infinitely variable transmission ratios that include forward and reverse ratios, or to provide some other benefits. The transmissions include multiple inner split pulleys nested within an outer split pulley. Two, three, or more inner split pulleys can be disposed within the transmission to balance the mass of the inner split pulleys in order to reduce vibration and internal stresses experienced by the transmission. This can increase the lifespan of the transmission, reduce wear, and increase efficiency. Additionally, providing multiple inner split pulleys in a nested configuration can allow for reduction of loads transmitted through bearings of the transmission.