Re: IML: proportioning valves

[Kenyon Wills <imperialist1960@xxxxxxxxx>]

Umm,

The major hydraulic brake difference between 1966 and
1967 Chrysler products is that the 67 has a dual
master cylinder with seperate circuits.  This happens
to be because they went to discs up front on some cars
and/or they saw the benefit of switching to dual MC's
across the entire line (so far as I know).

Discs require a different amount of fluid per stroke
to do their work, requiring a second reservoir on the
MC, and this is a safety benefit in terms of redundant
circuits.  

However, 1967 also saw the cars that kept 4 drums
equipped with dual MC as well, so this was a design
decision that was seperate (and perhaps driven by) the
fact that discs in front required a dual MC and THAT
had its benefits.

That or it was simply easier to manufacture a million
dual MC and machine them for disc or drum rather than
continuing to have a single MC and adding a dual as a
different casting?  

Or it was good design sense that made for good
marketing?

Or some combo of the above?

A proportioning valve balances two circuits out, so
that brakes are applied evenly at all 4 corners, or to
whatever bias you want applied (more front/more rear).
 Some aftermarket ones come with a knob so you can
tune your own bias.  

The Chrysler one in particular has a retarding action
on the rear circuit so that the fronts apply first and
the rears come on second and to a slightly lesser
degree so as to avoid rear-end lock-up in slippery
conditions as the car's weight transfers forward onto
the front axle.

The 1966 and prior cars do not have a Proportioning
Valve because they are a single pot master cylinder,
and the hydraulic pressure is applied evenly on all 4
wheels.  Or at least that's what I think here at work
computer and not looking at my 1966 in person.


I know this all because I did a sloppy job of
re-assembling my 1973 rear brakes on one corner during
a brake job and blamed the proportioning valve because
I was so certain the rear brake shoe assy's were
correct that I went after other stuff and bought a NOS
Proportioning valve for $250.  Hooray!

The peg that goes between the shoe and the wheel
cylinder was cock-eyed, so I'm now in posession of a
redone brake system and a really clean proportioning
valve that should last my lifetime and has the now
spare original unit hanging on the wall of my
workbench.




...The 63-66 drum brakes on imperials are absolutely
fabulous brakes and represent the apogee of drum brake
technology for large cars, I might add.



-Kenyon
 

Kenyon Wills
 
 






















      ____________________________________________________________________________________
Never miss a thing.  Make Yahoo your home page. 
http://www.yahoo.com/r/hs

-----------------  http://www.imperialclub.com  -----------------
This message was sent to you by the Imperial Mailing List. Please 
reply to mailing-list@xxxxxxxxxxxxxxxx and your response will be 
shared with everyone. Private messages (and attachments) for the
Administrators should be sent to iml.webmonster@xxxxxxxxx
To UN-SUBSCRIBE, go to http://imperialclub.com/unsubscribe.htm