[DeTomaso] Brake master plumbing
jderyke at aol.com
jderyke at aol.com
Wed Jul 20 13:27:52 EDT 2022
Dual circuit master cylinders are designed to have the rear piston- the one closest to the pushrod on the brake pedal- directly connected for quick response. The forward piston is actuated only by movement of the rear piston, with a small gap between them. So the more important front brakes are most quickly activated by the rearmost master cylinder port. And in most cases, the rearmost reservoir is larger in volume as befits the usually-larger front brake pistons which need more fluid. All logical but I would at least check that no proportioning was needed for the 6-piston rear brakes, especially since everything except the hard lines seems to have been changed. Maybe the builder got lucky?
-----Original Message-----
From: Julian Kift <julian_kift at hotmail.com>
To: Will Kooiman <will.kooiman at gmail.com>; Asa Jay Laughton <asajay at asajay.com>; detomaso at server.detomasolist.com <detomaso at server.detomasolist.com>
Sent: Wed, Jul 20, 2022 7:19 am
Subject: Re: [DeTomaso] Brake master plumbing
Correct, however the step bore (or more correctly quick take up) master
cylinder provides a means to get a large volume of fluid to the
calipers upon initial braking to take up the gap between rotor and pad.
This was a GM truck design to implement low drag pads to meet fuel
economy thresholds, the pads sitting further away from the rotor. The
larger bore is a small section on the master cylinder to effect that
initial take up, it is not a dual bore with independent proportioniong
function for front and rear circuits.
Julian
__________________________________________________________________
From: DeTomaso <detomaso-bounces at server.detomasolist.com> on behalf of
Will Kooiman <will.kooiman at gmail.com>
Sent: Wednesday, July 20, 2022 4:20 AM
To: Asa Jay Laughton <asajay at asajay.com>;
detomaso at server.detomasolist.com <detomaso at server.detomasolist.com>
Subject: Re: [DeTomaso] Brake master plumbing
I would think you're correct - larger rear outlet 1-3/8" goes to the
front, smaller front outlet 7/8" goes to the rear.
The front 6-piston has more surface area on the pads, so it needs a
bigger bore on the master.
But if it's all together, how does it drive? Is the proportioning
about right? Is there an external proportioning valve that might be
fixing the mismatch?
On 7/20/22, 1:42 AM, "DeTomaso on behalf of Asa Jay Laughton via
DeTomaso" <detomaso-bounces at server.detomasolist.com on behalf of
detomaso at server.detomasolist.com> wrote:
Hi all,
This brake master cylinder is installed in a Pantera with
Wilwood
six-piston brakes front and rear:
The master has a stepped bore. The larger at the rear measures
1-3/8"
and the front bore is smaller (probably 7/8" or an inch; I
forgot to
measure). The question is, which port on this master is
supposed to go
to the front brakes?
In my experience, most brake master cylinders of this type have
the
larger reservoir going to the front brakes, and the smaller to
the
rear. In my experience most masters of this type have the front
brakes
plumbed to the rear outlet (meaning the outlet closest to the
pedal
with the larger reservoir).
Since this is a non-stock installation, and I know some
variations can
mean the front brakes plumb to the front, I am curious which
port on
this master should go to which end of the car. I question this
because
I did not find this plumbed the way I expected, and maybe that
is fine.
This particular system may have been originally installed by
Bobby
Byars, who is unfortunately no longer available for
consultation.
I thank you in advance for your thoughts on this.
Thank you,
Asa Jay
--
Asa Jay Laughton - W7TSC, MSgt, USAFR, Retired
Spokane County ARES-RACES-ACS EC/RO
******************************
[1]https://w7tsc.org
[2]https://www.teampanteraracing.com
References
1. [1]https://w7tsc.org/
2. [2]https://www.teampanteraracing.com/
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4. http://server.detomasolist.com/mailman/listinfo/detomaso
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-------------- next part --------------
Dual circuit master cylinders are designed to have the rear piston- the
one closest to the pushrod on the brake pedal- directly connected for
quick response. The forward piston is actuated only by movement of the
rear piston, with a small gap between them. So the more important front
brakes are most quickly activated by the rearmost master cylinder port.
And in most cases, the rearmost reservoir is larger in volume as befits
the usually-larger front brake pistons which need more fluid. All
logical but I would at least check that no proportioning was needed for
the 6-piston rear brakes, especially since everything except the hard
lines seems to have been changed. Maybe the builder got lucky?
-----Original Message-----
From: Julian Kift <julian_kift at hotmail.com>
To: Will Kooiman <will.kooiman at gmail.com>; Asa Jay Laughton
<asajay at asajay.com>; detomaso at server.detomasolist.com
<detomaso at server.detomasolist.com>
Sent: Wed, Jul 20, 2022 7:19 am
Subject: Re: [DeTomaso] Brake master plumbing
Correct, however the step bore (or more correctly quick take up)
master
cylinder provides a means to get a large volume of fluid to the
calipers upon initial braking to take up the gap between rotor and
pad.
This was a GM truck design to implement low drag pads to meet fuel
economy thresholds, the pads sitting further away from the rotor. The
larger bore is a small section on the master cylinder to effect that
initial take up, it is not a dual bore with independent
proportioniong
function for front and rear circuits.
Julian
__________________________________________________________________
From: DeTomaso <[1]detomaso-bounces at server.detomasolist.com> on
behalf of
Will Kooiman <[2]will.kooiman at gmail.com>
Sent: Wednesday, July 20, 2022 4:20 AM
To: Asa Jay Laughton <[3]asajay at asajay.com>;
[4]detomaso at server.detomasolist.com
<[5]detomaso at server.detomasolist.com>
Subject: Re: [DeTomaso] Brake master plumbing
I would think you're correct - larger rear outlet 1-3/8" goes to the
front, smaller front outlet 7/8" goes to the rear.
The front 6-piston has more surface area on the pads, so it needs a
bigger bore on the master.
But if it's all together, how does it drive? Is the proportioning
about right? Is there an external proportioning valve that might be
fixing the mismatch?
On 7/20/22, 1:42 AM, "DeTomaso on behalf of Asa Jay Laughton via
DeTomaso" <[6]detomaso-bounces at server.detomasolist.com on behalf of
[7]detomaso at server.detomasolist.com> wrote:
Hi all,
This brake master cylinder is installed in a Pantera with
Wilwood
six-piston brakes front and rear:
The master has a stepped bore. The larger at the rear
measures
1-3/8"
and the front bore is smaller (probably 7/8" or an inch; I
forgot to
measure). The question is, which port on this master is
supposed to go
to the front brakes?
In my experience, most brake master cylinders of this type
have
the
larger reservoir going to the front brakes, and the smaller
to
the
rear. In my experience most masters of this type have the
front
brakes
plumbed to the rear outlet (meaning the outlet closest to the
pedal
with the larger reservoir).
Since this is a non-stock installation, and I know some
variations can
mean the front brakes plumb to the front, I am curious which
port on
this master should go to which end of the car. I question
this
because
I did not find this plumbed the way I expected, and maybe
that
is fine.
This particular system may have been originally installed by
Bobby
Byars, who is unfortunately no longer available for
consultation.
I thank you in advance for your thoughts on this.
Thank you,
Asa Jay
--
Asa Jay Laughton - W7TSC, MSgt, USAFR, Retired
Spokane County ARES-RACES-ACS EC/RO
******************************
[1][8]https://w7tsc.org
[2][9]https://www.teampanteraracing.com
References
1. [1][10]https://w7tsc.org/
2. [2][11]https://www.teampanteraracing.com/
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message posted here to all past, current, or future members of the
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or approve the archiving of list messages.
References
1. [16]https://w7tsc.org/
2. [17]https://www.teampanteraracing.com/
3. [18]http://server.detomasolist.com/mailman/listinfo/detomaso
4. [19]http://server.detomasolist.com/mailman/listinfo/detomaso
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9. https://www.teampanteraracing.com/
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