brake system components -
Hold-Off / Metering Valves are used in the front (disc) system of a disc/drum brake system. They provide a "hold off" function to allow the rear (drum) brakes to actuate first. This function is very important in making the system function in the correct sequence in a rear wheel drive car. The rear brakes are always actuated first. This function is built into most factory type disc/drum combination valves. Make sure you have a metering/hold-off valve in the system either as a stand alone valve or as part of a factory valve.
Valves go in the rear brake system (disc or drum) and provide
for control of the rate of pressure rise to the rear brakes -- just the
rate at which it builds up. Sooner or later the rear brakes see full master
cylinder discharge pressure. The purpose of this rate of pressure rise
control is to compensate for the reduction of weight on the rear wheels
due to forward weight transfer during braking. In short, it eases the
application of the rear brakes to help prevent rear wheel lockup. Factory
combination valves have these built in -- make sure you know what you're
getting, too little rate of rise is as bad as too much. You may not need
one of these valves depending on the compatibility of your vehicle's brake
Adjustable Proportioning Valves allow for fine tuning of the rate of pressure rise to the rear brakes if you have a lock up problem. If you have a lockup problem, experiment with the setting of the valve to eliminate lock up for all but all out panic stops. Good luck!
Residual Pressure Valves are used in a both front and rear brake system as follows: