The car suspension setting is always a trade-off between comfort and handling. The semi-active damper system seems to be an option for reducing the compromise between the two demands. This paper deals with the effect of the magnetorheological damper setting on a car’s suspension performance, especially tire grip, which was directly measured. A unique test rig was developed, and an experimental trolley with a fast magnetorheological damper (response time of 3 µs) was used in the paper. The damper was controlled by a modified Groundhook algorithm. Compared with the passive regime, the experiments showed a 30% improvement when using the Groundhook algorithm and when the damper was adequately set. The experiments proved the trends that were set by simulations.