[VAC] Re: Hydraulic-Actuated Electric Trailer Brake Controllers

["Dr. Gerald N. Johnson, electrical engineer" <geraldj@xxxxxxxx>]

I've seen that .02 cubic inch figure in Ford literature somewhere and
sometime in the past decade.

I suspect the drum/disk dual brake systems are a bit less sensitive to
volumetric unbalance because the drum and disk systems are inherently
less balanced than dual brake systems that use the same type of brake on
all four wheels. The volume to the disk brake cylinders is small because
their motion is small. The pads are barely retracted by the wobble of
the brake disk. The rear drum brakes though retract by springs to the
adjusters and if one doesn't drive in such a way to actuate the brake
adjusters there could be a significant liquid volume required. In my
experience, automatic brake adjusters that require a hard stop in
reverse don't adjust on flat gravel driveway and roads or with gentle
driving.

The .02 cubic inch figure probably applied specifically to dual brake
systems with identical brakes on all four wheels, and once invoked
continues to be applied to all brake systems to minimize owner
modifications of safety related brakes.

Gerald J.