Subject: Re: [Healeys] Drum to disc conversion - master cylinder change and a few questions

From: Alan Seigrist <[email-masked]>
Date: Tue, 17 Jan 2023 12:09:49 +0800

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Phil -

If you are going through that process, I would definitely get a Wilwood
dual master, this is much safer - if you have a hydraulic failure in the
front or back, the brakes will still work and you will be able to drive
home comparatively safely.

I don't know the weight balance between the front and back of your car, but
generally speaking if you put discs up front, you won't need to worry about
locking up the rear... drums usually take more effort to lock up than
discs.  You can put the discs on up front first, drive it a bit, and then
determine if the balance is right, then adjust if needed.  It's all about
the equipment on your car and the weight balance from front to back.

Also with discs, it's worthwhile to consider getting a brake servo, which
will make driving more pleasurable and give you better braking with
regular driving.

Best,

Alan

On Tue, Jan 17, 2023 at 10:26 AM Philip Fish <[email-masked]> wrote:

> 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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<div dir=3D"ltr">Phil -<div><br></div><div>If you are going through that pr=
ocess, I would definitely get a Wilwood dual master, this is much safer - i=
f you have a hydraulic failure in the front or back, the brakes will still =
work and you will be able to drive home comparatively safely.</div><div><br=
></div><div>I don&#39;t know the weight balance between the front and back =
of your car, but generally speaking if you put discs up front, you won&#39;=
t need to worry about locking up the rear... drums usually take more effort=
 to lock up than discs.=C2=A0 You can put the discs on up front first, driv=
e it a bit, and then determine if the balance is right, then adjust if need=
ed.=C2=A0 It&#39;s all about the equipment on your=C2=A0car and the weight =
balance from front to back.</div><div><br></div><div>Also with discs, it&#3=
9;s worthwhile to consider getting a brake servo, which will make driving m=
ore pleasurable and give you better braking with regular=C2=A0driving.<br><=
br>Best,</div><div><br></div><div>Alan</div></div><br><div class=3D"gmail_q=
uote"><div dir=3D"ltr" class=3D"gmail_attr">On Tue, Jan 17, 2023 at 10:26 A=
M Philip Fish &lt;<a href=3D"mailto:[email-masked]">[email-masked]</a=
>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0px=
 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><di=
v dir=3D"auto"><div dir=3D"ltr"><span style=3D"font-family:Arial,Helvetica;=
font-size:13px;background-color:rgb(255,255,255)">Hi all,=C2=A0</span><br s=
tyle=3D"font-family:Arial,Helvetica;font-size:13px"><span style=3D"font-fam=
ily:Arial,Helvetica;font-size:13px;background-color:rgb(255,255,255)">I&#39=
;m a long time Healey owner having had my BT7 for over 30 years.</span></di=
v><div dir=3D"ltr"><br></div><div dir=3D"ltr"><span style=3D"font-family:Ar=
ial,Helvetica;font-size:13px;background-color:rgb(255,255,255)">Recently I =
had a complete failure of a brake front drum (photos below) on my 1956 Jens=
en 541 (a 4ltr Austin powered contemporary of the Healey)=C2=A0</span><span=
 style=3D"font-family:Arial,Helvetica;font-size:13px;background-color:rgb(2=
55,255,255)">resulting in a total loss of my brakes.=C2=A0</span><span styl=
e=3D"font-family:Arial,Helvetica;font-size:13px;background-color:rgb(255,25=
5,255)">Not an experience I want to go through again. As a result I am look=
ing to do a drum to disc conversion using predominantly Healey parts=C2=A0<=
/span></div><div dir=3D"ltr"><br style=3D"font-family:Arial,Helvetica;font-=
size:13px"><span style=3D"font-family:Arial,Helvetica;font-size:13px;backgr=
ound-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 hu=
b 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.=C2=
=A0</span><br style=3D"font-family:Arial,Helvetica;font-size:13px"><br styl=
e=3D"font-family:Arial,Helvetica;font-size:13px"><span style=3D"font-family=
:Arial,Helvetica;font-size:13px;background-color:rgb(255,255,255)">I was wo=
ndering what the list subscribers have done to the MC and rear wheel cylind=
ers when you&#39;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 f=
it 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 con=
version 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 t=
o prevent any air getting into the wheel cylinders, but with a disk brake s=
et up this could cause brake drag.=C2=A0</span><br style=3D"font-family:Ari=
al,Helvetica;font-size:13px"><br style=3D"font-family:Arial,Helvetica;font-=
size:13px"><span style=3D"font-family:Arial,Helvetica;font-size:13px;backgr=
ound-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.=C2=A0=
</span><br style=3D"font-family:Arial,Helvetica;font-size:13px"><br style=
=3D"font-family:Arial,Helvetica;font-size:13px"><span style=3D"font-family:=
Arial,Helvetica;font-size:13px;background-color:rgb(255,255,255)">Currently=
 I have two 5/8&quot; wheel cylinders on the rear, four 1 1/4&quot; wheel c=
ylinders on the front and a 3/4&quot; master cylinder with a pretty small r=
eservoir. The system also incorporates a Lockheed 3:1 brake servo.=C2=A0</s=
pan><br style=3D"font-family:Arial,Helvetica;font-size:13px"><br style=3D"f=
ont-family:Arial,Helvetica;font-size:13px"><span style=3D"font-family:Arial=
,Helvetica;font-size:13px;background-color:rgb(255,255,255)">Any advice wou=
ld be appreciated.=C2=A0</span><br style=3D"font-family:Arial,Helvetica;fon=
t-size:13px"><br style=3D"font-family:Arial,Helvetica;font-size:13px"><span=
 style=3D"font-family:Arial,Helvetica;font-size:13px;background-color:rgb(2=
55,255,255)">Phil</span><div dir=3D"ltr"></div></div><div dir=3D"ltr"><span=
 style=3D"font-family:Arial,Helvetica;font-size:13px;background-color:rgb(2=
55,255,255)"><br></span></div><div dir=3D"ltr"><a href=3D"https://joc.org.u=
k/jensen-models/541-series/" target=3D"_blank">https://joc.org.uk/jensen-mo=
dels/541-series/</a></div></div>___________________________________________=
____<br>
rer" target=3D"_blank">http://www.team.net/donate.html</a><br>
<br>
Archive: <a href=3D"http://www.team.net/pipermail/healeys" rel=3D"noreferre=
r" target=3D"_blank">http://www.team.net/pipermail/healeys</a> <a href=3D"h=
ttp://autox.team.net/archive/healeys" rel=3D"noreferrer" target=3D"_blank">=
http://autox.team.net/archive/healeys</a><br>
<br>
<a href=3D"mailto:[email-masked]" target=3D"_blank">[email-masked]=
eam.net</a><br>
<a href=3D"http://autox.team.net/mailman/listinfo/healeys" rel=3D"noreferre=
r" target=3D"_blank">http://autox.team.net/mailman/listinfo/healeys</a><br>
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s/[email-masked]" rel=3D"noreferrer" target=3D"_blank">http://autox.t=
eam.net/mailman/options/healeys/[email-masked]</a><br>
<br>
</blockquote></div>

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From: Kees Oudesluijs via Healeys <[email-masked]>
Date: Tue, 17 Jan 2023 09:33:56 +0100

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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:
> 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.
>
> 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.
>
> Support Team.Nethttp://www.team.net/donate.html
> Archive:http://www.team.net/pipermail/healeys  http://autox.team.net/archive/healeys
>
> [email-masked]
> Unsubscribe/Manage:http://autox.team.net/mailman/options/healeys/[email-masked]
>

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<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
  </head>
  <body>
    <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:[email-masked]">
      <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) </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="">_______________________________________________

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