Turbomachine rotor blade and a turbomachine rotor

A turbomachine rotor includes a plurality of turbomachine rotor blades. The turbomachine rotor has a plurality of firtree shaped slots in its radially outer periphery to form a plurality of rotor posts. The turbomachine rotor blades have correspondingly shaped firtree roots to fit in the firtree shaped slots in the turbomachine rotor. The firtree roots of the turbomachine rotor blades comprise a plurality of radially spaced lobes on each of it flanks. The rotor posts of the turbomachine rotor comprise a plurality of radially spaced lobes on each of its flanks. A radially inner lobe of at least one of the turbomachine rotor blades has reduced stiffness such that the load on the radially inner lobe of the at least one turbomachine rotor blade is shared with the other lobes of the at least one turbomachine rotor blade. Alternatively a radially outer lobe of at least one of the rotor posts has reduced stiffness such that the load on the radially outer lobe of the at least one rotor post is shared with the other lobes of the at least one rotor post.