[Hcb3200]

for some a metering valve in this definition just holds pressure to keep the fluid from flowing back to master when no brake pressure is applied. It does not “meter” or change pressure to the brakes when applying pressure. You don’t need them as much when mounted on fire wall as this is above the brakes and fluid flows down. This keeps air from entering system when brakes are not applied. They are also call residual valves for residual pressure.

Proportions valves do what you posted keeps different pressures
Proportioning valves are frequently used in cars and other road vehicles to reduce the brake fluid pressure to the rear brakes. Due to weight distribution during heavy braking, more pressure is needed for front brakes. A proportioning valve reduces the pressure in the hydraulic lines to the rear brakes relative to that supplied to the front brakes during this heavy braking.


A combination valve does both and what most modern cars have that need them and it looks like a funny shaped brass hunk of metal.

The problem is most YouTube. Guys call the combination valve a proportioning valve. When it may be doing both and not one function. They make modern ones that just do the proportions.
And most don’t know that metering and residual are one and the same.