A method for assembling a double row angular contact rolling element bearing unit having an inner element with two raceways, and two separate outer ring pieces each with a single raceway, said outer ring pieces enclosing a gap which is wedge-shaped in a section through the bearing unit axis, and two series of rolling elements which are each accommodated between a raceway of the inner element and a raceway of an outer ring piece, tolerance means being provided between said outer ring pieces for urging said rings away from each other so as to provide the required tolerance (negative, zero or positive) to the bearing, said method comprises the steps of: providing an inner element having two raceways, providing two outer ring pieces each having a raceway, positioning the outer ring pieces around the inner element, positioning the series of rolling elements between the respective raceways of inner element and outer ring pieces, providing an endless tolerance ring, the cross-sectional dimensions of which are larger than the outer diameter of at least one of the outer ring pieces, shifting the tolerance ring up to a position opposite to the gap between the outer ring pieces, plastically deforming the tolerance ring so as to reduce the cross-sectional dimensions thereof and to provide the required tolerance between said tolerance ring and the opposing faces of the outer ring pieces which enclose the wedge-shaped gap.