An integrally bladed rotor for a gas turbine engine includes a hub, a plurality of blades radially extending from the hub and being integrally formed therewith. The hub having a rim from which the blades project and a pair of axially opposed split hub members extending at least radially inward from the rim. Each of the split hub members has a radially outer flex arm portion extending form the hub and a radially inner moment flange portion. At least one moment inducing element separately formed from the hub is mounted axially between the opposed split hub members and acts on the moment flange portions of the opposed split hub members to generate an inward bending moment on the flex arm portions of the opposed split hub members during rotation of the rotor, thereby deflecting the rim and the blades of the rotor radially inwardly.