Master Cylinder

For everyone, the linked article states for drum-drum brakes:

Drum brakes require a 10 lb. residual pressure (RPV10) to counteract the spring tension in the drum system which tends to pull the shoes away from the drums. This will give you a longer pedal travel and "spongy" brakes. The residual valve holds a pressure keeping the shoes near the drums giving a higher firmer pedal. Also required a metering valve (PVM) to the front (the metering valve prevents nose dive).


That doesn't jive with what I have read elsewhere. The "... to keep shoes near drum" sounds particularly strange. Our cars have "self-adjusters" that keep the shoes "tight enough". Wouldn't you always want the shoes to return to their mechanical stops, not resting against hydraulic pressure? I am just a mechanical engineer and these MBM guys are ? (shows old guy w/ handle-bar mustache). Anyway, decide for yourself what makes sense.

I understand that only rodders who place the MC below the floor need a residual valve today. Its purpose is to keep the rubber cups at the wheel cylinders tight so air doesn't get past them. The "new style" cup springs (say since 40 yrs ago) have a metal base (or tight-wound spring) that keeps the rubber tight, thus obviating a need for a residual valve in the MC.

The MBM suggestion of a metering valve for the fronts in drum/drum sounds confused also. I understand you only need a metering valve for a disk/drum setup. Its purpose is to hold off actuating the front disks until the rear drums have time (enough volume flow) to contact the shoes. Such a "front metering" is integral in later "combination valves". However, many people have no problem using just a proportioning valve for the rears in a disk/drum setup. Haven't heard of them complaining of "nose dive", but that probably requires a panic stop.

Similar to you, I rebuilt my brakes and want front disks eventually, but drums for now. I used a later disk MC & booster (for 95-99 Breeze) and the brakes work great.