A traction drive rotary assembly including a plurality of rolling elements having traction contact surfaces associating with each other to transmit power between the rolling elements. At least one of the traction contact surfaces has a surface microstructure including grooves and protrusions alternately arranged. The surface microstructure is represented by an unfiltered primary profile curve including recesses and projections corresponding to the grooves and the protrusions. Each projection includes a portion located higher than a center line of the unfiltered primary profile curve and having a shape selected from a generally trapezoidal shape with rounded corners, a generally crowning shape, a generally elliptic arc shape, a generally sinusoidal shape and a generally triangular shape with a rounded apex. A ratio .lambda./AMP of a wavelength .lambda. of the unfiltered primary profile curve to a half depth AMP of the recess is in a range of 50-400.
A method of forming a traction drive rolling element including: forming a preform having a working surface with an arcuate profile in section taken along a central axis; supporting the preform to be rotatable about the central axis; allowing a relative movement between the preform and a grooving tool for moving the grooving tool along the arcuate profile, simultaneously with rotating the preform about the central axis, to form microscopic recesses and projections alternately arranged in a direction perpendicular to the central axis along the arcuate profile; pressing a grindstone having a contact surface area of 25 mm.sup.2 or less, on the working surface; and allowing a relative movement between the preform and the grindstone for moving the grindstone along the arcuate profile simultaneously with rotating the preform while keeping pressing the grindstone on the working surface until a height of the microscopic projections becomes 3 .mu.m or less.
