The most important task of the tire is to ensure driving safety by optimally transmitting the required longitudinal and lateral driving forces. Although great progress has been made in the past in the development of new materials and patterns, many questions remain unanswered in the field of elastomer friction on rough surfaces. This is particularly true when an additional intermediate medium is introduced into the contact, as for braking on wet roads in the form of water. To better understand this process, a model of a single-tread block on a rough road surface is developed. The influence of the fluid is represented by a physical meaningful friction law. The model is validated with results of tire wet-braking tests on an internal drum test rig. The model can map the interaction between tire tread, rough road surface and fluid film and the simulation results show a good agreement with the measurement results. Based on the investigation of individual tread blocks, a new approach to the description of the wet-braking behavior of passenger car tires was thus demonstrated, which can be extended to more complex tread geometries in the future.