The results of a coupled-channels calculation for the elastic and inelastic scattering of 170 MeV ²³Na by ²⁰⁸Pb are compared with the adiabatic model and the isocentrifugal model. It is shown that, in the absence of Coulomb excitation, the tidal spin is conserved to a very good approximation. The effect of Coulomb excitation is to cause deviations from tidal symmetry. It is shown that the extent to which tidal symmetry is satisfied becomes very transparent if the amplitudes and analysing powers are calculated in a recoil frame where the recoil direction is chosen as the z axis.