In this study the flow field in the wake of a brake gap is analyzed using optical measurement systems, specifically 2D-2C Particle Image Velocimetry. The goal of the study is to show if a passive filtering method for brake particles is possible or not. Furthermore, the study aims to help understanding how particles, emitted by vehicle brakes, behave when they get manipulated aerodynamically. The first chosen method is an aerodynamic sheet, built inside a filter housing, in the wake of the brake. Measurements in the past indicated a significant pressure loss between the brake pad and the brake disk, lowering the efficiency of tested passive filtering systems. To regain the lost pressure the aerodynamic sheet is applied. A variety of sheet geometries and distances between the aerodynamic sheet and the brake disk are analyzed. The flow field is measured by a Particle Image Velocimetry (PIV) Setup with a pulsed laser and one camera (2C-2D PIV) installed around a brake test bench. The laser plane is placed perpendicular to the brake disk. The different velocity vector fields are then compared qualitatively to get an understanding how the pressure gradients behave. The results show a very strong boundary layer which is not detached from the brake disc. The thin layer of the flow near a surface where viscous forces cause the flow velocity to be identical to the surface velocity, due to the no-slip condition at the surface, is called boundary layer. The measurements show a low static pressure area behind the caliber, which is proved by a velocity field tending towards the caliper. Yet, a hypothetical passive filter mounted around the caliper would not be contaminated by particles. However, due to the aerodynamic sheets the boundary layer thickness increases, which indicates a reaction to the low pressure area. The second investigation uses a modified brake disc to alter the boundary layer. PIV measurements show the use of holes inside the brake disc to separate the boundary layer from the brake disc surface and by this enable a semi-passive filtering system. Ongoing research results show the reaction of a brake disc boundary layer to an injected air flow. The velocity fields show a significant flow reaction (vortex) with only little effort, which offers a big variety of possibilities for active filtering. The presented research activities give an understanding about the boundary layer of the brake gap flow and show new possibilities for altering this flow.