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Phil,
If you have a single brake system you better convert to a dual system
front/rear first.
I think I would change to front disk brakes only for the time being
leaving the rest as is and see what will be needed from there.
The brake pedal travel will increase because of the larger piston
surface area so it may or may not be necessary to change to a bigger
diameter MBC (which will increase pedal effort). In any case it will be
necessary to overhaul the MBC if it has been in operation for any length
of time as it may fail due to the ring of crud formed at the end of the
pistons travel.
If the rear brakes lock up to quickly fit rear wheel cilinders with a
smaller diameter or an adjustable pressure limiting valve on the rear
brakes. Another possibility may perhaps be to have the brake servo on
the front brakes only.
The pressure needed for the operation of front callipers also depends on
the total surface area of the calliper pistons. It may be well worth to
use after market 4 or 6 piston callipers from e.g Willwood or BCC
instead of the original A-H callipers.
Kees
Op 16-1-2023 om 23:14 schreef Philip Fish:
> Hi all,
> I'm a long time Healey owner having had my BT7 for over 30 years.
>
> Recently I had a complete failure of a brake front drum (photos below)
> on my 1956 Jensen 541 (a 4ltr Austin powered contemporary of the
> Healey) resulting in a total loss of my brakes. Not an experience I
> want to go through again. As a result I am looking to do a drum to
> disc conversion using predominantly Healey parts
>
> My car uses several components in common with the BN1, in particular
> it uses the same king pin/swivel axle set up. I have pretty much go
> the parts needed for the conversion (Denis Welsh Heavy Duty swing
> axles, AH 3000 steel wheel BTC101 hubs, taper bearings, disks and hub
> adapters etc) but I have some concerns about what changes I might need
> to make to the rest of the hydraulic system, particularly what changes
> I will need to make (if any) to the master cylinder and rear wheel
> cylinders.
>
> I was wondering what the list subscribers have done to the MC and rear
> wheel cylinders when you've converted the front drums to disks on your
> early cars. I believe that the front calipers need higher pressures
> (900psi) to operate than compared to the rear drums (400 psi) and was
> wondering if I need to fit some for of brake balance valve to stop the
> rears locking up before the fronts. Do you change the bore of the rear
> wheel cylinders when doing a conversion as an alternative? I have also
> read on the web that there may be a check valve in the MC which I
> might have to remove. Apparently with a drum brake set up the check
> valve retains some residual pressure after braking to prevent any air
> getting into the wheel cylinders, but with a disk brake set up this
> could cause brake drag.
>
> I would hate to do the conversion only to have worse brakes than my
> twin trailing shoe front drums that I have now.
>
> Currently I have two 5/8" wheel cylinders on the rear, four 1 1/4"
> wheel cylinders on the front and a 3/4" master cylinder with a pretty
> small reservoir. The system also incorporates a Lockheed 3:1 brake servo.
>
> Any advice would be appreciated.
>
> Phil
>
> https://joc.org.uk/jensen-models/541-series/
>
> _______________________________________________
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>
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<p>Phil,</p>
<p>If you have a single brake system you better convert to a dual
system front/rear first. <br>
</p>
<p>I think I would change to front disk brakes only for the time
being leaving the rest as is and see what will be needed from
there. <br>
</p>
<p>The brake pedal travel will increase because of the larger piston
surface area so it may or may not be necessary to change to a
bigger diameter MBC (which will increase pedal effort). In any
case it will be necessary to overhaul the MBC if it has been in
operation for any length of time as it may fail due to the ring of
crud formed at the end of the pistons travel.</p>
<p>If the rear brakes lock up to quickly fit rear wheel cilinders
with a smaller diameter or an adjustable pressure limiting valve
on the rear brakes. Another possibility may perhaps be to have the
brake servo on the front brakes only.<br>
</p>
<p>The pressure needed for the operation of front callipers also
depends on the total surface area of the calliper pistons. It may
be well worth to use after market 4 or 6 piston callipers from e.g
Willwood or BCC instead of the original A-H callipers.</p>
<p>Kees<br>
</p>
<div class="moz-cite-prefix">Op 16-1-2023 om 23:14 schreef Philip
Fish:<br>
</div>
<blockquote type="cite"
cite="mid:7F9FC5BF-7165-4547-81BE-2B7CB20F19B0@gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">
<meta http-equiv="content-type" content="text/html;
charset=UTF-8">
<span style="font-family: Arial, Helvetica; font-size: 13px;
-webkit-text-size-adjust: 100%; background-color: rgb(255,
255, 255);">Hi all, </span><br style="font-family: Arial,
Helvetica; font-size: 13px; -webkit-text-size-adjust: 100%;">
<span style="font-family: Arial, Helvetica; font-size: 13px;
-webkit-text-size-adjust: 100%; background-color: rgb(255,
255, 255);">I'm a long time Healey owner having had my BT7 for
over 30 years.</span></div>
<div dir="ltr"><br>
</div>
<div dir="ltr"><span style="font-family: Arial, Helvetica;
font-size: 13px; -webkit-text-size-adjust: 100%;
background-color: rgb(255, 255, 255);">Recently I had a
complete failure of a brake front drum (photos below) on my
1956 Jensen 541 (a 4ltr Austin powered contemporary of the
Healey)Â </span><span style="font-family: Arial, Helvetica;
font-size: 13px; -webkit-text-size-adjust: 100%;
background-color: rgb(255, 255, 255);">resulting in a total
loss of my brakes. </span><span style="font-family: Arial,
Helvetica; font-size: 13px; -webkit-text-size-adjust: 100%;
background-color: rgb(255, 255, 255);">Not an experience I
want to go through again. As a result I am looking to do a
drum to disc conversion using predominantly Healey
parts </span></div>
<div dir="ltr"><br style="font-family: Arial, Helvetica;
font-size: 13px; -webkit-text-size-adjust: 100%;">
<span style="font-family: Arial, Helvetica; font-size: 13px;
-webkit-text-size-adjust: 100%; background-color: rgb(255,
255, 255);">My car uses several components in common with the
BN1, in particular it uses the same king pin/swivel axle set
up. I have pretty much go the parts needed for the conversion
(Denis Welsh Heavy Duty swing axles, AH 3000 steel wheel
BTC101 hubs, taper bearings, disks and hub adapters etc) but I
have some concerns about what changes I might need to make to
the rest of the hydraulic system, particularly what changes I
will need to make (if any) to the master cylinder and rear
wheel cylinders. </span><br style="font-family: Arial,
Helvetica; font-size: 13px; -webkit-text-size-adjust: 100%;">
<br style="font-family: Arial, Helvetica; font-size: 13px;
-webkit-text-size-adjust: 100%;">
<span style="font-family: Arial, Helvetica; font-size: 13px;
-webkit-text-size-adjust: 100%; background-color: rgb(255,
255, 255);">I was wondering what the list subscribers have
done to the MC and rear wheel cylinders when you've converted
the front drums to disks on your early cars. I believe that
the front calipers need higher pressures (900psi) to operate
than compared to the rear drums (400 psi) and was wondering if
I need to fit some for of brake balance valve to stop the
rears locking up before the fronts. Do you change the bore of
the rear wheel cylinders when doing a conversion as an
alternative? I have also read on the web that there may be a
check valve in the MC which I might have to remove. Apparently
with a drum brake set up the check valve retains some residual
pressure after braking to prevent any air getting into the
wheel cylinders, but with a disk brake set up this could cause
brake drag. </span><br style="font-family: Arial, Helvetica;
font-size: 13px; -webkit-text-size-adjust: 100%;">
<br style="font-family: Arial, Helvetica; font-size: 13px;
-webkit-text-size-adjust: 100%;">
<span style="font-family: Arial, Helvetica; font-size: 13px;
-webkit-text-size-adjust: 100%; background-color: rgb(255,
255, 255);">I would hate to do the conversion only to have
worse brakes than my twin trailing shoe front drums that I
have now. </span><br style="font-family: Arial, Helvetica;
font-size: 13px; -webkit-text-size-adjust: 100%;">
<br style="font-family: Arial, Helvetica; font-size: 13px;
-webkit-text-size-adjust: 100%;">
<span style="font-family: Arial, Helvetica; font-size: 13px;
-webkit-text-size-adjust: 100%; background-color: rgb(255,
255, 255);">Currently I have two 5/8" wheel cylinders on the
rear, four 1 1/4" wheel cylinders on the front and a 3/4"
master cylinder with a pretty small reservoir. The system also
incorporates a Lockheed 3:1 brake servo. </span><br
style="font-family: Arial, Helvetica; font-size: 13px;
-webkit-text-size-adjust: 100%;">
<br style="font-family: Arial, Helvetica; font-size: 13px;
-webkit-text-size-adjust: 100%;">
<span style="font-family: Arial, Helvetica; font-size: 13px;
-webkit-text-size-adjust: 100%; background-color: rgb(255,
255, 255);">Any advice would be appreciated. </span><br
style="font-family: Arial, Helvetica; font-size: 13px;
-webkit-text-size-adjust: 100%;">
<br style="font-family: Arial, Helvetica; font-size: 13px;
-webkit-text-size-adjust: 100%;">
<span style="font-family: Arial, Helvetica; font-size: 13px;
-webkit-text-size-adjust: 100%; background-color: rgb(255,
255, 255);">Phil</span></div>
<div dir="ltr"><span style="font-family: Arial, Helvetica;
font-size: 13px; -webkit-text-size-adjust: 100%;
background-color: rgb(255, 255, 255);"><br>
</span></div>
<div dir="ltr"><a
href="https://joc.org.uk/jensen-models/541-series/";
moz-do-not-send="true"
class="moz-txt-link-freetext">https://joc.org.uk/jensen-models/541-series/</a></div>
<br>
<fieldset class="moz-mime-attachment-header"></fieldset>
<pre class="moz-quote-pre"
wrap="">_______________________________________________
Archive: <a class="moz-txt-link-freetext"
href="http://www.team.net/pipermail/healeys";>http://www.team.net/pipermail/healeys</a>
<a class="moz-txt-link-freetext"
href="http://autox.team.net/archive/healeys";>http://autox.team.net/archive/healeys</a>
<a class="moz-txt-link-abbreviated"
href="mailto:Healeys@autox.team.net";>Healeys@autox.team.net</a>
<a class="moz-txt-link-freetext"
href="http://autox.team.net/mailman/listinfo/healeys";>http://autox.team.net/mailman/listinfo/healeys</a>
</pre>
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