Proportioning valve

[1] Any valve which limits pressure in a system, e.g., in a hydraulic circuit, in automatic transmissions, in pneumatic suspension systems, etc.
[2] The valve used in the rear brake line of some cars with front disc and rear drum brakes. When braking gently, pressure is about equal front and rear; as pedal pressure is increased, the limiting valve controls and finally limits pressure to the rear wheels to prevent rear wheel lockup during heavy braking. The British term for "proportioning valve" is "pressure limiting valve". See brake proportioning valve, load-sensitive proportioning valve, regulated proportioning valve