Top: residual tangential velocity with respect to the Hyades group motion, as a function of the distance to the cluster centre, for a selected Monte Carlo simulation of field white dwarfs as described in the text. The red points are cool white dwarfs with M_V > 12. The horizontal dotted line represents the residual velocity upper limit of 8 km s^-1 used in Sect. 5.1. Bottom: same simulation as the top panel, but corrected for the completeness of the WDC (see Sect. 5.3).