The kinematic layout is an essential part in the early development phase of an automotive door. Apart from the door opening mechanism, the main focus lies on the synthesis of the window lifter, which has a high impact on the glass shape and on window tightness properties. The main task is to find a proper window motion with respect to the space requirements and the maximum seal deflection. Boundary conditions are given by the shape of the pillars and the window which are mainly styling driven. In this contribution a method is described to compute an optimized motion allowing for all such restrictions. The applied method is based on a CAD platform and combines simulation with parametric-associative design. This leads to a high level of flexibility and simple handling. The presented approach is an example of an upfront design analysis significantly supporting the door development process.