  Fragment kinetic energy spectra for reactions induced by 8.0 GeV/c
$\rm{\pi^-}$ beams incident on a $\rm{^{197}}$Au target have been analyzed in
order to deduce the possible existence and influence of thermal expansion. The
average fragment kinetic energies are observed to increase systematically with
fragment charge but are nearly independent of excitation energy. Comparison of
the data with statistical multifragmentation models indicates the onset of
extra collective thermal expansion near an excitation energy of E*/A
$\rm{\approx}$ 5 MeV. However, this effect is weak relative to the radial
expansion observed in heavy-ion-induced reactions, consistent with the
interpretation that the latter expansion may be driven primarily by dynamical
effects such as compression/decompression.
