A method for operating a medical probe includes pressing a distal end of the medical probe, which includes one or more arms that extend diagonally outward from a central shaft and have respective position transducers coupled thereto, against an intra-body surface, so as to cause the arms to exert pressure on the surface and bend with respect to the central shaft in response to the pressure. Positions of the respective position transducers coupled to the arms are measured, and the pressure exerted by the arms is estimated responsively to the measured positions.