Over the past decades, Vascular Interventional Surgery Robots (VISR) have been developed to address the risks associated with X-rays used in minimally invasive vascular surgery procedures. Manipulation of over-the-wire catheters is necessary to perform complex surgery but requires high forces on the robot's end effector during rotational movements. The VISR under study mimics the physician's fingers by rolling the catheter between two planar surfaces to rotate it. In this study, an experimental set-up is used to replicate this grasping method, also used in other VISR [1, 2]. The parameters of the gripping surfaces are investigated to maximise the torque delivered to the catheter and minimise the forces required at the robot's end-effector. The implemented design of experiment (DOE) demonstrated that large and soft gripping surfaces could achieve this compromise. By adjusting these parameters, sufficient torque can be achieved on the catheter.