  We have investigated the detailed torque-reversal behavior of 4U 1626--67 in
the framework of the recently developed comprehensive model of the inner disk
radius and torque calculations for neutron stars accreting from geometrically
thin disks. The model can reproduce the torque -- X-ray luminosity relation
across the torque reversals of 4U 1626--67. Our results imply that: (1)
rotational equilibrium is reached when the inner disk radius equals the
co-rotation radius, $r_\mathrm{co}$, while the conventional Alfven radius is
greater than and close to $r_\mathrm{co}$, (2) both spin-up and spin-down
torques are operating on either side of torque reversal, (3) with increasing
accretion rate the spin-up torque associated with accretion onto the star
gradually dominates the spin-down torque exerted by the disk. The torque
reversals are the natural outcome of transitions between the well-defined
weak-propeller and spin-up phases of the star with a stable geometrically thin
accretion disk.
