| Perhaps one of our engineers could do the numbers on this, to see what
| the bias is. Nelson?
|
| Dick Taylor
|
|
OK guys, I'm Electrical Engineer and there's no electronics in the brakes,
but that doesn't stop me from talking about what I don't know about.
The most important point is that the pressure in the front and back is the
same --- otherwise the PWDA would move to one side.
The problem is that sometimes the front brakes need more fluid like if the
pads are kicked back with a loose hub (BTDT, pedal goes the floor). Other
times the rear need more fluid, especially if they are out of adjustment.
Also recall that there are two sizes of rear cylinders but only one type of
MC. There must be some automatic adjustment.
The key is that the front MC piston is pushed forward by the rear piston
using the hydraulic fluid between the pistons that also goes to the front
brakes --- hence the pressure on both sides of the system are the same and
the varied fluid requirements are achieved automatically by the varying
movement of the forward piston as required to keep the pressure constant.
The fluid systems are separate in the master cylinder. If the rear piston
(for the front brakes) looses all fluid, it can still be pushed far enough
forward to run into and push the forward piston to apply the rear brakes.
(Not sure that'll help much in stopping, but the screeching will warn others
to get out of the way.) If the forward piston (rear brakes) looses all
fluid, it will be pushed to the mechanical stop that will then allow
pressure to then build behind it for the front brakes.
There is a spring between the two pistons and between the front piston and
the front of the cylinder to center the forward piston properly when the
pedal is released.
After many years of wondering I finally sat down and figured this out while
waiting for the power coating on my MC to cool this spring (it's great to be
unemployed). Another really neat scheme.
Nelson Riedel
Granville Ohio
'68TR250, '70TR6, '76TR6
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