[urq] Rear 'proportion valve'

[Ben Swann]

Frank,  I'll keep this in mind.  I checked the IST docs as well, but did not see any
reason that would preclude me from going with a simple Wilwood proportioning valve.

Here is what I have ordered and received:
Rebuilt Hydrualic Brake booster - installed
V8 rear calipers(with pads of course) and rotors - already installed
New brake lines all aroud.
Choice of the two master cylinders - early 23mm and later 25mm also used on the 5000 TQ
(specified heavy duty and wagon).
Wilwood Rear Proportioning valve
Porche Monoblock 4 pot calipers - from 993 I think, never did confirm, but got correct
pads as well, by matching the pads.

I was tempted to get a stock proportioning valve replacement since they are dirt cheap a
RockAuto on closeout, but just did not seem to be a better option than the adjustable.

I may do this job tommorrow, since I am once again deadlocked on the V8 transmission
swap into 200Q [ job from #[=!!.]

Question:  While trying to figure out which proportioning valve to use, I noticed the
choice of 2 in 4 out valves and other variations.  Why, where would one use this - is
there a simple single out Master that one could conceivably adjust proportion to all
corners?

Also, I installed the one-man bleeder valves in the calipers.  They seemed to work fine,
but did not seal well without a fair amount of tightening - read "enough that I might be
ringing the threads or doing damage".  Any experience on these?  I got them from
Pep-Boys (HELP products IIRC).

Ben

[Date: Fri, 12 Nov 2010 09:13:45 +0000
From: "fdekat" <fdekat at sentex.net>
Subject: [urq] Rear 'proportion valve'
To: urq at audifans.com
Message-ID: <201011121413.oACEDjtr097003 at smarthost1.sentex.ca>
Content-Type: text/plain; charset=iso-8859-1


THat 'proportion valve' that a lot have been discussing lately, in conjunction with
Ben's brake problems:

If you read the IST documents  that Martin has stashed on his web site (www.quattro.ca),
there is a good explation as to how that valve works.

It does nothing, until the rear brake circuit reaches a set pressure, then limits the
rear circuit to that pressure.  (Also has a mechanisim to give rear brakes full line
pressure, if front braking pressure is lost)

At 'less than heavy stops', I'm thinking that it has no effect, so perhaps keep that in
mind when doing your problem dignostics. (See chart inthe IST| docs). Thoughts?

As those 'rear line limit valves' are notorious for leaking, the Tilton setup sounds
like a good alternative.

I'm curious as to exactly what that valve does or how it works?  Does it just
(adjustably) limit the rear line pressure (as the stock piece), or does it variably
modify the rear line pressure as a percentage of the front line pressure? 


Regards,

=Frank de Kat=
]