The modeling of magnetorheological dampers combines the use of the laws of physics along with a phenomenological description. The phenomenological models that are used to describe these devices present a symmetric hysteresis loop. However, the experimental hysteresis loops of MR dampers are not symmetric. To take into account this asymmetry, we propose a modi cation of the viscous + Dahl model, use the modi ed model to describe a large-scale magnetorheological damper, and validate the modi ed model against experimental data.