We have investigated the effect of tip flexibility on stick–slip dynamics, treating themotion of the tip apex and the cantilever within a Langevin description. Wehave found that the dynamical system, which includes the cantilever and the tipapex, exhibits a rich variety of regimes of motion depending on the values of thedissipation constants associated with the translational motion of the apex and thebending motion of the tip. The proposed model explains the fine structure of thestick–slip patterns and the wide variation of slip durations, between microseconds andmilliseconds, observed in recent experiments with a friction force microscope (Maier et al 2005 Phys. Rev. B 72 245418). The results of our full Langevin description arecompared with the predictions of the single-spring Prandtl–Tomlinson model andthe hybrid Langevin–Monte Carlo approach, which has recently been proposed.