Abstract: An adjustable handlebar mounting assembly adapted to mount above the head tube of a bicycle frame includes a pair of inserts, each of which has a generally cylindrical inner surface formed and adapted to at least in part encircle the bicycle steerer tube. Each of the inserts has a generally arcuate exterior surface, the axis of which is generally perpendicular to the axis of the generally cylindrical interior surfaces. There is a front cap and a back cap, each of which has an interior surface which mates with the exterior surface of an insert. Fasteners secure the caps together and in tight engagement with the exterior of the inserts. A stem extension tube is attached to the front cap and a handlebar is mounted to the stem extension tube. The mating surfaces of the inserts and caps are adjustable in their relative positions, whereby the position of the caps relative to the inserts and the bicycle frame, and thus the angle of the stem extension relative to the frame, is adjustable.