The disclosure relates to a belt pulley decoupler for transmitting torque between the belt of a belt drive and a shaft in driving connection therewith. The belt pulley decoupler includes: a hub fastened to the shaft, a belt pulley rotatably mounted on the hub, a helical torsion spring arranged in a torque flow path between the belt pulley and the hub, a first spring plate extending in the torque flow path on a side of the belt pulley, and a second spring plate rotationally fixed to the hub.
The hub has an imbalance which compensates for an imbalance of the helical torsion spring resulting from a ground portion of the spring ends in such a way that the following relationship applies for the spring imbalance {right arrow over (U)}s and the hub imbalance {right arrow over (U)}b: |{right arrow over (U)}s+{right arrow over (U)}b|