Originally posted by canadianal
if you have a double resivoir type master you will need one in each line . if drums 10 lbs if disks in the front a 2 lb in the front and ten in the rear.
what i have been told it is to keep backpressure in the lines as the brake cylinders can pull air back in after application and let off.
i put them in my bucket and they seenm to work
for rear drums, a 10# will keep the wheel cylinder pistions from compleatly retracting into the bore, which if they did, would cause a soft pedal due to the shoes being too far in, air has no factor in them, because if there was any air in the system, you could feel it at the pedal. an aftermarket master cyl would need at least the 10 # in the rear circut for the drums but an OEM would have the 10 # built in. the front 2 # keeps fluid from reterning to the master cylinder resivore if the master cylinder is the lowest point of the cylinder, a 10 # on a disc brake circut will cause brake drag.