"The adj prop valve is designed to restrict pressure to the rear brakes to keep them from locking up, he can't get them to lock up! So putting a restrictor in the system will do absolutely nothing but make it worse."
A proportioning valve can be adjusted
to the point where the rear brakes grab
first. It only restricts the flow if you
want it to.
The valve is needed to fine tune
the brake bias. It's purpose is to
restrict reaction time. The first hit
on the brakes during a panic stop
should, for a fraction of a second
restrict the transfer of vehicle weight
(bias) to the front. Holding the weight
transfer back. Tire contact and springs
play a major role here. Too little
contact and a soft front spring
will result in rear tire lock up when
trying to stop 3800 lbs of momentum.
The weight wants to nosedive into
The system on my build from a blank
slate is cobbled together from different
vehicle manufacturers. Ford Granada
front rotors and calipers, Jeep rear
rotors, Ford Explorer rear calipers,
Mopar master cylinder w/1.031 bore,
Chrysler Le Baron dual booster, 2lb
residual check valves in each line,
adjustable proportioning valve
to the rear, 1/8 ID steel brake lines,
Vehicle weight is 3100 lbs., brake
pedal ratio 4:1. First time in with
no components swapped out,
or trying to diagnose poor braking
She stops on the proverbial dime,
and does lock up all four in the event
of an "oh sh*t" occurrence.
Bare in mind, this system never
existed before. All parts are new
and ordered as seperate components.
KD, hopefully you can gleen some info
from what is posted. Cars of old have
always had brake "lock up". And back
then, reading the skid marks on the
pavement gave a pretty good
indication as to each wheels braking
performance by the marks they left,
and most mechanics could "feel" the
bias of a properly functioning brake
Which, evidently, makes you a pretty
good mechanic, as the brake bias
you are experiencing just isn't quite
Me, 47 years as a mechanical Engineer...
My brakes work as required.