An arrangement for measuring distortion in cylinders. A sensor projects straight out of the end of a motion-transmitting arm. The arm can be both translated and rotated. The sensor accommodates a probe that probes the geometry of the surface of the cylinder. The sensor has a distortion-measuring structure accommodated in the head of a surface-geometry probe and a check for axially secured and undeflected tensioning of the probe. The probe is an elongated geometry-probing pin. The structure is securely tensioned remote from the chuck in the vicinity of a structure-attachment section in the head. The structure includes at least one zone of attenuation between the chuck and the structure-attachment section and has a resilient section and a strain gauge.