The present invention resides in a wheel bearing unit (100) having an inner member (105) and an outer member (107) rotationally coupled to each other by at least one row of rolling elements (115), whereby at least one bearing inner ring (110) is mounted on the inner member (105). The inner member (105) comprises a first section (130) and a second section (135) that at least party lies radially inward of the first section (130). According to the invention, the first section (130) is formed from a first material and the second section (135) is formed from a metal material, preferably a lightweight metal such as aluminium. The second section (135) of the inner member (105) is joined to the first section (130) by means of a semi-solid metal process, and to ensure a radial interlock between the first and second sections (130, 135), the first section comprises a portion (140) extending in a radially inward direction, wherein the portion presents at least one surface that faces away from the bearing axis of rotation (X). Thus, as the semi-solid metal of the second section (135) cools, it has a surface against which to radially contract, thereby ensuring a permanent join and long service life of the unit (100).