I was service manager for the Western US when the pressure valves were being
installed as production items. They worked, but the customers complained
ALL THE TIME that their front brakes were dragging (so they thought). This
may have been the cause of the demise of this valve. Most of the shop people
just didn't understand what it was and why and so when the car was jacked up
and the wheels were tight from the last brake application they thought
something was wrong and so took out the valve to please the customer who
then came back with the "knock-off" problem. The valve also created a little
difficulty in bleeding out the system which also the shop dealer people
never got a handle on even after repeated shop bulletins and instructions.
The trick in the bleeding for those that have a valve in their system NOW,
is:
You must first bleed the system before the valve , then immediately after
the valve before bleeding the balance of the system. Kind of a pain cause
there is no bleeder on the valve but, just back off the connecting fitting a
bit and bleed as normal.
----- Original Message -----
From: "Randall Young" <Ryoung@navcomtech.com>
To: "Fot" <fot@autox.team.net>
Sent: Tuesday, September 09, 2003 8:36 AM
Subject: RE: TR6 Axle Mod
> > As an adjunct to this, I also wondered whether anyone has investigated
the
> > possibility of plumbing in a 3-5 PSI residual pressure valve in the
front
> > line to ensure that the disk pads are kept up against the disk rotors?
>
> When the TR3 switched to front discs, the factory started installing
> residual pressure valves for just that reason. They were deleted some
time
> during TR4 production, I don't know why. Perhaps it was because tighter
> recommended clearances reduced the problem, or maybe it was just a
> cost-cutting measure.
>
> Perhaps I'm missing something, but it seems to me that the proposed
> modification would be valid, even if one chose to still run some
clearance.
> There would still be some knock-back due to the clearance of course, so as
> with most things it's a trade-off.
>
> Zero clearance or even a slight pre-load should also be easy to measure,
by
> assembling with a "checking shim" of known thickness and measuring the end
> float. Subtracting the shim thickness from the measurement gives the
> clearance or pre-load.
>
> Not that it's all that hard to come up with a suitable torque gauge, all
you
> need is a lever arm and a weight.
>
> Just my $.002, YMMV
> Randall
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