A camshaft phaser is provided for varying the phase relationship between a crankshaft and a camshaft in an engine. The camshaft phaser includes a stator having lobes. A rotor disposed within the stator and rotatable between a full retard position to a full retard position includes vanes extending radially outward from a central hub and interspersed with the stator lobes to define alternating advance and retard chambers. A first portion of the central hub between adjacent vanes extends radially outward further than a second portion of the central hub between adjacent vanes.