We present results on the effect of the stiffness of the equation of state on the dynamical bar-mode instability in rapidly rotating polytropic models of neutron stars in full General Relativity. We determine the change in the threshold for the emerg
ence of the instability for a range of the adiabatic $Gamma$ index from 2.0 to 3.0, including two values chosen to mimic more realistic equations of state at high densities.
