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4 wheel disk brake conversion HELP needed
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vinnybagadonuts
Posted 2018-07-30 11:51 PM (#567472)
Subject: 4 wheel disk brake conversion HELP needed


Member

Posts: 7

Location: Nashua NH
Calling all brake gurus any ideas? I did a 4 wheel disc conversion on a 56 royal lancer using AAJ rear kit and ECI front. All GM calipers, Large single piston front, smaller single piston rear. 11" rotors. I had 1 1/8" bore manual MC from Master Power set up for all discs and it did not work. I had to pump the brakes to get any pedal then it would stop, but no panic stops it pretty much just goes to the floor if just press it once slow or fast. I tested the master it was fine. Bled the brakes like crazy still crappy pedal.

I called AAj and he suggested 15/16 MC for increased pressure. I bought a Mopar A body MC from rock auto and pulled the residual valve from the rear port of the master since discs don't need those. But I have the same problem. still need to pump them a few times to get a pedal

I isolated the issue to the front calipers by pinching the hoses to the front calipers and the pedal is high and firm. I bled them to death and still the same issue. I have to pump the pedal 3 times to get a pedal. It is a volume thing? Im just about to drive the car into a wall at this point.

Any Ideas would be much appreciated
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mikes2nd
Posted 2018-07-31 1:05 AM (#567477 - in reply to #567472)
Subject: Re: 4 wheel disk brake conversion HELP needed


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I think you need more volume.

good info here...

http://www.forwardlook.net/forums/forums/thread-view.asp?tid=68535&...

do you have an adjuster? If not your going to need one. Those front calipers need alot of fluid, 15/16 would make it worse.
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mstrug
Posted 2018-07-31 5:03 AM (#567488 - in reply to #567472)
Subject: Re: 4 wheel disk brake conversion HELP needed



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Location: Newark, Texas (Fort Worth)
Are the bleed ports on top or bottom of the calipers? The 'A' body MC is for dual disc? There are disc/disc MC's out there.


Edited by mstrug 2018-07-31 5:06 AM
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vinnybagadonuts
Posted 2018-07-31 11:11 AM (#567506 - in reply to #567477)
Subject: Re: 4 wheel disk brake conversion HELP needed


Member

Posts: 7

Location: Nashua NH
mikes2nd - 2018-07-31 1:05 AM

I think you need more volume.

good info here...

http://www.forwardlook.net/forums/forums/thread-view.asp?tid=68535&...

do you have an adjuster? If not your going to need one. Those front calipers need alot of fluid, 15/16 would make it worse.


Thanks for the info. I tend to think the same but I also tried a 1 1/8" and it had the same problem.

yes I'm using a SSBC distribution block with adjuster to the rear breakes

Edited by vinnybagadonuts 2018-07-31 11:27 AM
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vinnybagadonuts
Posted 2018-07-31 11:17 AM (#567507 - in reply to #567488)
Subject: Re: 4 wheel disk brake conversion HELP needed


Member

Posts: 7

Location: Nashua NH
mstrug - 2018-07-31 5:03 AM

Are the bleed ports on top or bottom of the calipers? The 'A' body MC is for dual disc? There are disc/disc MC's out there.


Yes the A body MC 15/16" had the rear residual valve removed from the port so it is modified for all disc use.

Also all the bleed ports are straight up, I even tried removing the front calipers and rotating them slightly and bleeding them with a block of wood in place of the rotor to make sure the bleeders were perfectly clocked straight up
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ttotired
Posted 2018-07-31 4:55 PM (#567519 - in reply to #567472)
Subject: Re: 4 wheel disk brake conversion HELP needed



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Location: Perth Australia
I would find out exactly what the calipers are off and get the mc off that to either look at or buy but you said yo locked off the front and got a good pedal
try locking off the back and 1 front, then just the back.

You said you had a volume problem with the 1 1/8, then went smaller, you need to try bigger and I assume boosted

The other way is callipers with a smaller piston

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vinnybagadonuts
Posted 2018-07-31 11:42 PM (#567549 - in reply to #567472)
Subject: Re: 4 wheel disk brake conversion HELP needed


Member

Posts: 7

Location: Nashua NH
Thanks I'm leaning to a mopar power brake MC 1 1/8 bore. All the info has been helpful
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brand209
Posted 2019-03-08 1:56 PM (#579037 - in reply to #567472)
Subject: Re: 4 wheel disk brake conversion HELP needed


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Posts: 60
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I had the same problem when I went to all wheel disc on my 72 dart, bought a willwood mc with a bigger bore and solved the problem
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mikes2nd
Posted 2019-03-08 4:20 PM (#579045 - in reply to #567472)
Subject: Re: 4 wheel disk brake conversion HELP needed


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Posts: 3531
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Bore and stroke/throw are all part of the equation. I would look at the GM master cylinder for those calipers. But more than likely those were with drum brakes so you need to calculate for the rear discs, it's going to be alot of guessing unless you get a whole system, then it has to be mapped to the throw of the brake pedal on your car, you can get an adjustable rod to maybe adjust the throw also.
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mikes2nd
Posted 2019-03-08 4:25 PM (#579046 - in reply to #567472)
Subject: Re: 4 wheel disk brake conversion HELP needed


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Posts: 3531
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https://web.archive.org/web/20080122132034/http://www.jakelatham.com...

Here is An old calculator, not sure it can still work
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mikes2nd
Posted 2019-03-08 4:28 PM (#579047 - in reply to #567472)
Subject: Re: 4 wheel disk brake conversion HELP needed


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Posts: 3531
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http://www.wallaceracing.com/brake-master-cyl-calc1.php

https://www.wilwood.com/mastercylinders/mastercylinderlanding

 

&nbs
ders/mastercylinderlanding

 

 

 




Edited by mikes2nd 2019-03-08 4:34 PM
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60 dart
Posted 2019-03-08 5:53 PM (#579049 - in reply to #567472)
Subject: Re: 4 wheel disk brake conversion HELP needed



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Location: WHEELING,WV.>>>HOME OF WWVA
did you try it "with" the residual valve ? uh , just try it!------------------------------------------------------later

Edited by 60 dart 2019-03-08 5:55 PM
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