Dual master cylinder for drum brakes

[mbmd57]

Found a dual master cylinder for 4 wheel drum brakes NMC22125 1 1/8" bore for Kelsey Hayes under dash booster no need for a portion valve. Question which port on the M/C should go to the front brakes? 

[KYBlueOval]

I'm no brake expert, but it is my understanding that the larger reservoir is always for the front brakes. So connect to the port for that reservoir.
Did the instructions suggest you bench bleed the MC before installing? If not I'd suggest you do that.
Let's see what others on the Forum have to say, they are more knowledgeable.
John

[gasman826]

Also, many Ford masters had larger fitting for front brake circuit.

[KULTULZ]

If the MC is an original FORD (BENDIX) drum/drum design, the rear reservoir supplies the front brakes and the front reservoir supplies the rear brakes (each reservoir being equal in size). Other car manufacturers sometimes had it reversed, so the MC has to be spec'd for FORD. What vehicle did you spec the MC for?

You must make sure the replacement MC has RESIDUAL VALVES in both outlet ports. This being an aftermarket off-shore unit, it is difficult to figure so you have to read the manufacturer's instruction sheet very carefully.

You may also have brake line size differences which may require adapter fittings.

You must get back after successful install as I am curious how it will all work out.

[59meteor]

1 1/8" bore sounds pretty large for a manual brake application, or do you have power brakes? Typically, a manual brake master cylinder has similar sized reservoir chambers, disc brake usually has one chamber much larger than the other, the large chamber is for the front disc brakes, to allow for displaced fluid as the front pads wear and get thinner, causing the pistons to extend. Also keep in mind, a manual brake master will have a pushrod between the brake pedal and master pistons, that is "captured" by a clip, to prevent the brake pedal from swinging back far enough to allow the pushrod to fall out of the piston, causing no brakes. A power master has just a hole in the rear piston, which engages into a pushrod inside the vacuum booster.

[mbmd57]

I did a search for 1 1/8" dual master for 4 wheel drum brakes and found that number NMC-22125 Oreillys also Raybestos MC36355 its for a 1967 Ford F350 truck uses the same wheel cylinders F 1 1/8 R 15/16 The 15/16 is on the Skyliners, Wagons and Rancheros I have a Skyliner. On Monday I will call Raybestos abut the ports I believe you are correct about the rear port to the front brakes.     

[KULTULZ]

The OP has 57/59 SWIFT-SURE POWER BRAKE

I did a search for 1 1/8" dual master for 4 wheel drum brakes and found that number NMC-22125 Oreillys also Raybestos MC36355 its for a 1967 Ford F350 truck uses the same wheel cylinders F 1 1/8 R 15/16 The 15/16 is on the Skyliners, Wagons and Rancheros I have a Skyliner.

On Monday I will call Raybestos abut the ports I believe you are correct about the rear port to the front brakes.

You did your research ... 

Make sure you ask them about the RESIDUAL PRESSURE VALVS install on the outlet ports. You will have a soft pedal without them.

Please get back as to the results.

[rmk57]

 
  Can you see the rubber duckbill residual valves without pulling out the seat out from the master?

[geraldchainsaw]

i'm watching this post as i still have the orig style MC,    so  far the NMC 22125 is sounding good for a replacement,  i don't have anyone doing my work for me,  so what i need to know is,  is this a shoe in other then reworking the brake lines,   or is it more involved,  thanks,   jerry

[KULTULZ]

 
Can you see the rubber duckbill residual valves without pulling out the seat out from the master?

You may or may not. Take a paper clip and insert an open end gently into the outlet post(s). If you feel like a rubber (bouncy) resistance, that should be the valve. If no resistance, no valve.

[KULTULZ]

i'm watching this post as i still have the orig style MC,    so  far the NMC 22125 is sounding good for a replacement,  i don't have anyone doing my work for me,  so what i need to know is,  is this a shoe in other then reworking the brake lines,   or is it more involved,  thanks,   jerry

It is fairly straight forward far as plumbing, unless you decide to use a PRESSURE DIFFERENTIAL VALVE.

You have power brakes, correct?

I am assuming the outlet ports on this MC are on the outboard side.

[mbmd57]

As stated above I have the under dash power brake booster made by Kelsey Hayes for 57-59 cars you can use a 1" MC but it will require more pedal pressure than the 1 1/8" when I receive the dual MC I will check for the residual valves.

[lowrider]

Also, many Ford masters had larger fitting for front brake circuit.

I picked up a 61 Starliner a few years ago where the PO had installed power brakes with a dual master cylinder. Don't know what master cylinder he used but he ended up using a larger size brake line coming out of the master cylinder then an adapter to fit the lines on the car. Car stopped "ok" but I didn't like all extra plumbing so I decided to install a master cylinder with the correct lines. After I finished it and took it for a ride I couldn't believe how much better it stopped. That was just one of the many things I've had to redo on this car. Another never ending project.

[alvin stadel]

i'v been reading all the post on and about the brakes, On my 57 RHT the breaks are as original.  Sure swift power assist, everything is new , lines , cylinders.  I have adjusted and bled the brakes 4 or 5 times and am still having trouble getting it to stop. Now this morning I read that  the front wheel cylinders should be 1 1/8 and the rear 15/16.  Is this true where I do not have a dual master cylinder. This  is about ready to drive me nuts.

[brushwolf]

Is it not the general rule that a larger diameter mc bore will always require more pedal force exerted upon it than a smaller bore mc - but with less travel; and a smaller bore mc will require less pedal force exerted upon it than a larger bore mc - but requires greater travel to displace an equal amount of fluid? 

And the force exerted by your foot is amplified by the further distance of the brake rod pin from the pedal pivot point on a manual brake pedal, or by the booster assist on a power brake system?

But since there are actually two mc pistons in series in a dual reservoir mc, doesn't that mean you are asking your booster to do a bigger job ( x 2 ), than a single piston in the original single reservoir mc? Seems to me like that would tend to give a hard pedal without a larger booster and it seems this has been proven repeatedly by people using 6 and 7 inch firewall mounted boosters. The KH booster is only 5" in diameter, so that is even less boost it would seem.

But, I am also planning to utilize my KH booster (though with front disks), so I am interested in seeing how this works out before I order a new mc.  The limited brake pedal arm travel of the 57-59 Swift Sure system as originally designed would seem to be a factor in dropping the bore size down, but so would the boost power of the KH booster when pushing essentially two 1 1/8" mc pistons.

Any incorrect assumptions I have laid out there?