  Using a high resolution N-body simulation of a two-component dwarf galaxy
orbiting in the potential of the Milky Way, we study two effects that lead to
significant biases in mass estimates of dwarf spheroidal galaxies. Both are due
to the strong tidal interaction of initially disky dwarfs with their host. The
tidal stripping of dwarf stars leads to the formation of strong tidal tails
that are typically aligned with the line of sight of an observer positioned
close to the host center. The stars from the tails contaminate the kinematic
samples leading to a velocity dispersion profile increasing with the projected
radius and resulting in an overestimate of mass. The tidal stirring of the
dwarf leads to the morphological transformation of the initial stellar disk
into a bar and then a spheroid. The distribution of stars in the dwarf remains
non-spherical for a long time leading to an overestimate of its mass if it is
observed along the major axis and an underestimate if it seen in the
perpendicular direction.
