  We study the dissipative evolution of (0+1)-dimensionally expanding media
with Bjorken symmetry using the Boltzmann equation for massive particles in
relaxation-time approximation. Breaking conformal symmetry by a mass induces a
non-zero bulk viscous pressure in the medium. It is shown that even a small
mass (in units of the local temperature) drastically modifies the well-known
attractor for the shear Reynolds number previously observed in massless
systems. For generic nonzero particle mass, neither the shear nor the bulk
viscous pressure relax quickly to a non-equilibrium attractor; they approach
the hydrodynamic limit only late, at small values of the inverse Reynolds
numbers. Only the longitudinal pressure, which is a combination of thermal,
shear and bulk viscous pressures, continues to show early approach to a
far-off-equilibrium attractor, driven by the rapid longitudinal expansion at
early times. Second-order dissipative hydrodynamics based on a gradient
expansion around locally isotropic thermal equilibrium fails to reproduce this
attractor.
