This paper presents experimental results and a modelling study of a prototype mechanical device that represents a novel steering compensator for high-performance motorcycles. The mechanical device is different from conventional damper devices since it has been designed to represent a series combination of a damper and an inerter. The ideal inerter is a one-port mechanical element which is the exact analogue of the capacitor under the force-current analogy between mechanical and electrical networks, so that the force (torque) through the device is proportional to the relative acceleration (angular acceleration) across its terminals. The steering compensator is tested on a hydraulic test rig and the experimental admittance of the device is calculated over a specified frequency range. A model of the device is developed, including parasitic effects and nonlinearities, which achieves a good fit between model and experimental data.