Compressor wheel assembly

A compressor wheel assembly comprises a compressor wheel (7) mounted to a rotating shaft (8), extending through a bore (21) provided along the rotational axis of wheel (7). The bore (21) has an inner diameter greater than the outer diameter of the shaft (8) and a cylindrical sleeve (22) is located concentrically around the shaft (8) to thereby support the shaft (8) co-axially within the bore (21).