Proportioning Valve: Description
WARNING: This page is about a different car, the 2007 Kia Optima, 2007 Kia Magentis, 2006 Kia Optima, and 2006 Kia Magentis. However, it is still accessible from the selected car via links, so may be relevant.
Do not disassemble the proportioning valve. The proportioning valve makes the ideal distribution of fluid pressure to the front and rear brakes to prevent the brakes from skidding in the event of rear wheel lock up and to obtain higher brake efficiency within the range of service brake application.