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Possibility of using an OE single piston MC with front discs
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56D500boy
Posted 2022-03-07 12:54 PM (#620075)
Subject: Possibility of using an OE single piston MC with front discs



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I am currently working towards front discs on my 56 Dodge D500 with 12 x 2.5 Chrysler Center Plane brakes. In the *SHORT* run, I would like to run the OE MC with the new front calipers. I think that it might work but I am hoping for some feed back. I measured the diameter of the MC piston at 1.125" and the Center Plane wheel cylinders at 1 5/16" (1.3125"). The calipers that I am looking at would have 2.50" pistons. Using a spreadsheet that Del S. sent me sometime ago (thanks Del), I think I have done the math to conclude that it could work.

That said, my assumptions about wheel cylinder and caliper piston travel might be wrong. (??)

A screen shot of the spreadsheet:


Edited by 56D500boy 2022-03-07 1:38 PM




(EstimatingUtilityOfOEMasterCylinderWith56DodgeD500BrakesAndFrontCalipers.jpg)



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Attachments EstimatingUtilityOfOEMasterCylinderWith56DodgeD500BrakesAndFrontCalipers.jpg (101KB - 139 downloads)
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dels56
Posted 2022-03-07 2:42 PM (#620077 - in reply to #620075)
Subject: Re: Possibility of using an OE single piston MC with front discs


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Hi Dave, I see a number of car here that have discs on front and still using the OE master cylinder. Saw a 55 Chev on Saturday that had discs all around and a single compartment master. The question is... why?
Put discs on for better braking and safety. The dual compartment master is another safety feature.

Del S
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56D500boy
Posted 2022-03-07 3:29 PM (#620079 - in reply to #620077)
Subject: Re: Possibility of using an OE single piston MC with front discs



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Why? Because I am still working on this (below) (but it is a few weeks/months down the road and I could just be days away for the front disc brakes if I temporarily use the OE MC)

REFERENCE:

http://www.forwardlook.net/forums/forums/thread-view.asp?tid=75197&...

Staying with the single channel MC would only be temporary, not permanent.



Edited by 56D500boy 2022-03-07 4:24 PM
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geoffs60
Posted 2022-03-07 3:45 PM (#620080 - in reply to #620077)
Subject: Re: Possibility of using an OE single piston MC with front discs


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Interesting looking at the results most have had with disc conversions. Almost all complaining that the recommended 1" bore MC that will clear the bellows booster will not bleed up and give a confident pedal, likewise on a 57 dodge I experienced the same issue. I resorted back to the 1 1/8 single MC and got a perfect pedal and great braking. The callipers over wheel cyls require more fluid and to get volume with a limited travel you need bore size to achieve this. Like wise as with most comments a dual circuit is preferable with safety in mind, but finding an 1 1/8 MC of this design to clear the booster isn't available off the shelf, unless you modify a dual circuit MC and machine the reservoir down to clear the booster which is one option I have considered.
The one issue I have been aware of is a little drag after use with the discs, it does clear in time and I wonder if the residual pressure in the orig style 1 1/8 MC is little high to what a disc brake system should have ? can anyone share any light on this.?
To date i have used the AAJ kit over the scarebird kit, in NZ no steering or brake components are allowed any welded items in any part of the car, additionally with the AAJ kit I use the 70-71 B/E 11" rotors, does away with the inner adaptor and allows use of the orig inner bearing/seal assys.
On another note has anyone had experience fitting disc brakes on a 1955 chrysler/desoto - these have the 3 bolt spindles.
Thanks Geoff
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56D500boy
Posted 2022-03-07 4:19 PM (#620081 - in reply to #620080)
Subject: Re: Possibility of using an OE single piston MC with front discs



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geoffs60 - 2022-03-07 12:45 PM
On another note has anyone had experience fitting disc brakes on a 1955 chrysler/desoto - these have the 3 bolt spindles.


Thanks for your comments and experience Geoff.

As for your question, AAJ had (has?) a bracket kit for the 3 bolt 55 Chrysler/Desoto spindles:



Edited by 56D500boy 2022-03-07 4:23 PM




(WP_20141122_007a.jpg)



(WP_20141122_006a.jpg)



(WP_20141122_005a.jpg)



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Attachments WP_20141122_007a.jpg (180KB - 132 downloads)
Attachments WP_20141122_006a.jpg (205KB - 136 downloads)
Attachments WP_20141122_005a.jpg (213KB - 133 downloads)
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Powerflite
Posted 2022-03-07 7:03 PM (#620084 - in reply to #620075)
Subject: Re: Possibility of using an OE single piston MC with front discs



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Dave, I have run the original masters with disc brakes on many of my cars for many years without any issue. I expected to find the discs dragging, but never did. They were always rotating freely. Just go for it, it shouldn't be an issue.

I'm curious why you chose to use the '75 New Yorker booster. What was your criteria to choose that particular one? I need to get a '55 booster & master for one of my cars, but I am considering just doing as you are doing here instead, if I can't find a suitable solution. I take it you were unable to find a newer booster than didn't require drilling new holes?

Edited by Powerflite 2022-03-07 7:06 PM
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56D500boy
Posted 2022-03-07 7:37 PM (#620086 - in reply to #620084)
Subject: Re: Possibility of using an OE single piston MC with front discs



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Thanks for the vote of confidence (on the single channel OE MC - for the short term), Nathan.

Before I went down the front disc rabbit hole, my game plan was to install the high mount 55 Mopar PB pedal system with the 75 Chrysler booster and my OE (actually a Raybestos replacement) MC.

It's been a while since I made the decision to go with the 75 Chrysler booster but as I remember it, the bolts for the MC were normal Mopar and the booster would fit on the 55 Chrysler firewall plate (with minor redrilling for the booster) and the booster size (distance from the firewall and diameter) wasn't too too big. That said, there were going to be issues with the voltage regulator (which will go away if/when I go to a bird cage Mopar alternator and small external mechanical regulator).

Once I got that sorted I was going to go with the drum/drum MC, maybe using your "trick" distribution block plug.

Once the dust settled on all that, then and only then, was I going to entertain the idea of front discs. and a disc/drum MC.

Unfortunately, I bumped into the Scarebird 57-61 Mopar front disc brackets (that Scarebird doesn't think would work on a 56 Chrysler/Desoto (they still don't know that they will - I haven't told them yet)) . Never one to back away from a challenge (and too pig-headed to fail and give up), I am now down the front disc rabbit hole and I don't feel like quitting until I can at least drive the car with them on.

ALL THAT SAID, Del S. sent me this photo from Arizona, showing a 55 Desoto with a small PB booster and some Drum/Drum MC (looks like a GM thing - which I would hope to avoid). He was going to search out the owner and get details. No success there, yet.





Edited by 56D500boy 2022-03-07 11:08 PM
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JBLKEN
Posted 2022-06-14 6:40 AM (#622126 - in reply to #620075)
Subject: RE: Possibility of using an OE single piston MC with front discs


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Great info!! I'm about to wake up my 55 Desoto from it's 4+ year sleep. I'm having an auto restore guy come to my home Thrsday to evaluate/estimate putting a front disc brake kit onto the 55 Desoto Sportsman that I have owned 54 years (also service it - at 85 years I no longer time to do the work on my cars ). The kit I have was designed and produced, by an individual, for his 55 Chrysler. He evidently made extra sets and sold them on eBay - that was over 10 years ago! Between me and my friend we together bought 3 sets. I was wondering if I could keep by original single PW MC (even though I have a dual MC that I have no idea, at present, if it will fit. I'm doing the brake conversion just for one last long distance tour into the Sierras, in Oct, with my preteen grand kids (and their dad), after which I will put the car back to sleep again.

Ken Wilson
San Jose, Calif
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