It is known that the way a bicycle or motorcycle rider grasps the handlebar may have implications on the bike stability. Indeed, the rider closes a loop (with his/her hands) between the front assembly and the chassis of the bike, which in turn affects the open-loop stability of the vehicle. The aim of this paper is to experimentally quantify the interaction between the rider and the handlebar through the frequency response function (FRF), and to numerically simulate the effects of such interaction on the bicycle stability. In order to implement the effect of rider’s arms/hands, a mechanical model is employed to fit the experimental FRFs. The parameters of a number of different riders have been derived and used to assess the effect on bike dynamics.