[SARBlade]

I was watching a video on proportioning valves, now I'm in the know! They are really not proportional at all but a relief valve. Drum brakes are extremely efficient at applying stopping power on little pressure where as disc brake requires much more pressure to apply stopping power to its disc. The relief valve in a drum setup is used to release pressure at a set point as to not "lockup" the wheel by the person applying the pressure and potentially losing control of the vehicle. The disc setup requires more pressure, like 10 x the amount a drum requires for the same stopping power, so there is not really a requirement for a relief valve on disc setups. This is as I now understand it. Please correct me if I'm wrong. Thanks

I'm just adding to my post so its clear, the idea of the metering of pressure is so the rear brakes have pressure when stopping, if they don't and all the pressure is applied at the front, then there could be some ass passing ground looping happening.