The ventilated brake disk represents the state of the art in braking technology for passenger cars. Since other vehicle requirements are usually dominant, the cooling of such disks becomes a problem. In order to optimize the disk brake cooling and reach a compromise relative to these other requirements, the air flow to and through the disk is simulated. To accomplish this, the whole wheel housing is modeled as a three dimensional domain using the general purpose computational fluid dynamics (CFD) code STAR-CD.The analysis is described and the results are shown to be reasonable. They provide a new fundamental insight into the behaviour of the disk air flow which is of great interest in understanding the overall air flow. Various methods of visualization facilitate both local and global correlation. Simulations for a few geometric modifications are also presented and provide a good estimate of the potential for improving the cooling.