Variable geometry turbocharger with guide pins

A variable geometry turbocharger assembly (10) comprises a unison ring (18) which rotates about a longitudinal axis defined by a shaft (24) on which a turbine wheel (26) and compressor wheel are attached in order to pivot a plurality of vanes (20) and thereby control a flow of exhaust gas to the turbine wheel. The unison ring (18) rotates on at least one guide pin (16) which is secured to the turbocharger. The guide pins (16) may be press-fit into apertures (54) in a center housing (14) at an outer pilot surface. In other embodiments the guide pins (16) may be press-fit into a different part of the turbocharger such as a nozzle ring. The guide pins (16) may each have a wear surface which defines a circumferential radius of curvature which is substantially equal to a circumferential radius of curvature of a radially inner surface of the unison ring (18).