A transmission with a continuously variable adjustable ratio comprising a first disk fixedly coupled to a first shaft, and a second disk coupled for a rotation about the axis of the first disk. A second shaft is supported for rotation about an axis essentially parallel to the face of the first disk wherein said axis is supported in a tilted position relative to the planar face of the first disk such that the distance between said axis and the first disk planar face increases from said disk center to said disk edge. An idler is coupled for rotation about and axial movement along each second shaft and is in frictional contact with the first disk face. A pinion is fixedly coupled to each second shaft and interconnects with the face of the second disk. Thus, idler axial movement along the second shaft varies both the relative rotational speeds between the first and second disks and the frictional contact pressure between the idler and the first disk face. The relative size of idler to pinion determines the ranges of ratios achieved. The transmission has low frictional losses and is therefore highly efficient, thereby extending service life.