Mass M vs. equatorial radius R_eq diagram and spin-up tracks of the two pulsars. The colour code and the numbers labelling the tracks correspond to the ones used in Figs. 3 and 6. For comparison relations between the mass and the equatorial radius of equilibrium configurations are shown for f = 0 and 300 Hz. The large open-star symbol corresponds to the PSR J1614−2230 configuration and the small one to PSR J0751+1807.