A wet disc brake system is described which includes a housing assembly and brake callipers. The housing assembly is provided with openings for seating cylinders of respective brake callipers. The callipers are coupled to a structural component of a vehicle to which the system is fitted and in particular a flange of an axle housing. This enables reactive forces created during a braking operation to be transmitted via the callipers to the flange and axle housing rather than being carried by housing assembly. As the housing assembly does not bear any substantive load, it may be made of a relatively light weight construction or material.