dual master cylinder

[joe in ma.]

I am instaling a dual reservoir master cylinder in my 41 pu having trouble finding part number for bolt on top master all I can find are spring top masters do not think I have enough clearance for it under the floor

[busmania]

I bought one from posies that installed with a small plate adapter. They were helpful when I was at that stage of my project. Give em a call and I’m sure they can point you in the right direction.

[alchemy]

Roadster Supply now has a dual master with the three bolt flange that mounts right to a stock old Ford bracket. Can’t tell you if you’ll need to modify the opening in your floor though.

[TJ]

Originally Posted by joe in ma.

I am instaling a dual reservoir master cylinder in my 41 pu having trouble finding part number for bolt on top master all I can find are spring top masters do not think I have enough clearance for it under the floor

I used the Corvette master cylinder which has a low top with the spring that holds it on. It cleared the floor in my '40 with no problem. I also used the same in my '41 pickup.

[Ron_r1959]

I used the corvette master in my 41 pickup as well with a adapter, I am not saying its the most accessible filling it but its no biggie either. I did install a disc brake conversion onto the original spindles, and used the original style rims. When it was all done I had to extend the rod a little bit, probably because of the adapter I suppose.

[51504bat]

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An other option


Early ford 3 bolt master cylinder w/dual reservoirs



https://carrillocustoms.com/collecti...ual-reservoirs

[Ron_r1959]

Wish I had found that when I did mine LOL

[V8COOPMAN]

Originally Posted by Ron_r1959

Wish I had found that when I did mine LOL

Yup, that is a much-needed modification for those seeking to run a dual M/C. It's kind of unfortunate that they built it with a 1" diameter bore, as the originals (as far as I know) are 1-1/16" diameter bore. This means that the stroke of the pedal will need to be longer to displace an equal volume of brake fluid to match the original M/C. This could introduce issues with possibly running out of available pedal travel, and especially so if one circuit of the cylinder develops a leak.

It is safe to say that when one circuit with these dual M/Cs develops a leak, the brake pedal must travel a greater distance than normal to move the same volume of fluid as when the front or rear circuits have NO leaks. You can look at the dual M/C below closely to understand WHY the physics in these M/Cs dictates that they operate in this manner.

If you'll study the drawing below and pay particular attention to the green-colored circuit with leak, as well as understanding exactly which cups are creating the pressure to move fluid, you'll see why MORE piston travel is necessary in a dual M/C if one side develops a leak.

Coop

[pbsdaddy]

What car? I have a 35 2 door slant back and a twin pot mounted in a relatively normal place above the steering column. Sorry, I can't post pics.

[coolcoupe]

very well explained, Coop

[alchemy]

Originally Posted by pbsdaddy

What car? I have a 35 2 door slant back and a twin pot mounted in a relatively normal place above the steering column. Sorry, I can't post pics.

Nothing normal about that in an early Ford. He can get where he needs to be with simple parts and maybe some small adapters. No need for big fabrication.

[V8COOPMAN]

Originally Posted by pbsdaddy

What car? I have a 35 2 door slant back and a twin pot mounted in a relatively normal place above the steering column. Sorry, I can't post pics.

pbsdaddy ..... I came up with this tutorial (click link BELOW) a while back to help F'Barners with posting pictures on this forum. It obviously helped another new 'Barn member just last night. Click the link BELOW!

https://www.fordbarn.com/forum/showp...&postcount=649

Coop


.

[V8 Bob]

Originally Posted by V8COOPMAN

Yup, that is a much-needed modification for those seeking to run a dual M/C. It's kind of unfortunate that they built it with a 1" diameter bore, as the originals (as far as I know) are 1-1/16" diameter bore. This means that the stroke of the pedal will need to be longer to displace an equal volume of brake fluid to match the original M/C. This could introduce issues with possibly running out of available pedal travel, and especially so if one circuit of the cylinder develops a leak.


Coop

I agree the pedal travel will be longer with a 1" master, but can be used safely with stock Ford pedals if care is taken to minimize floor covering below/around the pedal, and pedal arm bumper thickness to allow max travel. I'm using modified '34 and stock '40 pedals with 1" masters, and have full master cylinder travel.
Bob

[1948F-1Pickup]

The movement increase is about 3/8" at the master when comparing the larger bore master of 1 1/16" and the greater amount of piston movement with the smaller bore master of 1 inch. (0.866" piston travel in the 1 1/16" bore to move 1 cubic inch of brake fluid vs 1.27" piston travel in the 1" bore to move 1 cubic inch of brake fluid)

With that extra 3/8" AND the pedal ratio, you might very well bottom the brake pedal into the floorboard on some vehicles/applications.
It wasn't a problem on my '48 truck but it just underscores that you wouldn't know the true story unless you did the math.

[V8COOPMAN]

Originally Posted by 1948F-1Pickup

The movement increase is about 3/8" at the master when comparing the larger bore master of 1 1/16" and the greater amount of piston movement with the smaller bore master of 1 inch. (0.866" piston travel in the 1 1/16" bore to move 1 cubic inch of brake fluid vs 1.27" piston travel in the 1" bore to move 1 cubic inch of brake fluid)

With that extra 3/8" AND the pedal ratio, you might very well bottom the brake pedal into the floorboard on some vehicles/applications.
It wasn't a problem on my '48 truck but it just underscores that you wouldn't know the true story unless you did the math.

That's interesting that you actually took the time to calculate the additional travel required of the M/C's piston to displace the necessary volume of brake fluid. My main concern was to make it obvious to folks that may not be familiar with what we're talking about here, as well as the POSSIBILITIES of what can happen if you're not aware.

The math that I am seeing here doesn't tell the ENTIRE story. If you subtract 0.866" from 1.27", that leaves an ADDITIONAL distance of 0.404" that the PISTON must travel. That is not the main concern. You must also take pedal travel into account. This means that the pedal pad (the part that your foot pushes on) must travel a GREATER distance which is dependent on the pedal ratio. Pedal ratio involves the difference in the distance of the pushrod pivot pin from the pedal-pivot centerline vs. the distance that the pedal pad is from the pedal-pivot centerline. If the pedal footpad is five (or more) times farther from the pedal pivot point, the pedal RATIO is 5:1. That means that the pedal PAD must be able to travel FIVE TIMES the ADDITIONAL DISTANCE that the piston must travel. In this case, we're talking about an additional 2.02" PEDAL TRAVEL.

BEWARE.....as this does NOT INCLUDE any additional pedal travel necessary as I referenced ABOVE because of a leak in one side of the system. All that I am suggesting here is that it should be wise to induce a "test leak" in each side of your newly-plumbed brake system to insure that you still have full-stroke-pedal capabilities should a leak develop in either side of your system. Also beware that "full stroke" means WITHOUT THE M/C BOTTOMING-OUT. The M/C should NOT bottom-out.

Coop


.

[Mart]

Personally I have used single circuit cylinders in my cars in recent years. Coops spells out the issues in his post above. Retrofitting a cylinder to an old fashioned car like our early fords is probably not a great idea.
Repeating what coops has already said, dropping to a 1" cylinder will mean you need all the available travel. When a dual circuit brake system fails on one side, you need extra travel before the brakes on the good side can be applied. The chances are you will not have enough travel.
I do have a dual cylinder on my roadster. It is 1-1/16" from an E250 van. It is a big old cylinder though, much bigger than the 1" cylinders often used. It fixed my excessive travel problem but I have never tested if it would work if one side failed. I suspect it would not.
I prefer the simplicity of the single circuit and ensure the system is maintained in good order. I also ensure the hand (emergency) brake is also in good working order.
In summary I believe swapping to a dual cylinder is not necessary, may impair brake "feel" and may not give the intended advantage of maintaining some braking in the event of a failure.
Just my opinion.

[1948F-1Pickup]

Originally Posted by V8COOPMAN

The math that I am seeing here doesn't tell the ENTIRE story. If you subtract 0.866" from 1.27", that leaves an ADDITIONAL distance of 0.404" that the PISTON must travel. That is not the main concern. You must also take pedal travel into account. This means that the pedal pad (the part that your foot pushes on) must travel a GREATER distance which is dependent on the pedal ratio. Pedal ratio involves the difference in the distance of the pushrod pivot pin vs. the distance that the pedal pad is from the pedal's pivot centerline. If the pedal footpad is five (or more) times farther from the pedal pivot point, the pedal RATIO is 5:1. That means that the pedal PAD must be able to travel FIVE TIMES the ADDITIONAL DISTANCE that the piston must travel. In this case, we're talking about an additional 2.02" PEDAL TRAVEL.

BEWARE.....as this does NOT INCLUDE any additional pedal travel necessary as I referenced ABOVE because of a leak in one side of the system. All that I am suggesting here is that it should be wise to induce a "test leak" in each side of your newly-plumbed brake system to insure that you still have full-stroke-pedal capabilities should a leak develop in either side of your system. Also beware that "full stroke" means WITHOUT THE M/C BOTTOMING-OUT. The M/C should NOT bottom-out.

Coop


.

That is true..... hence my mention of "that extra 3/8" AND the pedal ratio.
Almost any re-designer of a brake system should be looking at total stroke
available for the pedal assembly and comparing it to total stroke available
of the master. Few people do this, that is why few people should be modding
brake systems.

[V8 Bob]

Originally Posted by 1948F-1Pickup

The movement increase is about 3/8" at the master when comparing the larger bore master of 1 1/16" and the greater amount of piston movement with the smaller bore master of 1 inch. (0.866" piston travel in the 1 1/16" bore to move 1 cubic inch of brake fluid vs 1.27" piston travel in the 1" bore to move 1 cubic inch of brake fluid)

With that extra 3/8" AND the pedal ratio, you might very well bottom the brake pedal into the floorboard on some vehicles/applications.
It wasn't a problem on my '48 truck but it just underscores that you wouldn't know the true story unless you did the math.

Gonna have to disagree with some of the above math.

1" master cylinder piston travels 1.27" for 1 c.i. of fluid movement.

1 1/16" master cylinder piston travels 1.12" for 1 c.i. fluid movement.

The 1" piston travel increase is .150", or just over 1/8", not 3/8". This results in pedal travel increase of .750" with a 5:1 ratio, or .9" with a 6:1. As I stated previously, using a 1" is doable in most cases with minimum effort. The resulting higher pressure output with a 1" works better with common disc/drum systems by slightly lowering the pedal effort.
I know converting to a dual master cylinder is the best hydraulic brake upgrade you can make, but does require some thought and extra effort.

[rich b]

Well if you are going to use a 1" dual master on the stock pedal assembly operating Lockheed brakes, you better see how it does with a simulated failures of either the front or rear brakes; then consider how it would do if the brakes were worn some and not recently adjusted.

Mart's 1-1/16" E250 master cylinder is a good alternative; but is physically larger and will require a bulge in the floorboard cover. In my case I made a wood die and pressed a cover in my press.

[petehoovie]

Originally Posted by rich b

Well if you are going to use a 1" dual master on the stock pedal assembly operating Lockheed brakes, you better see how it does with a simulated failures of either the front or rear brakes; then consider how it would do if the brakes were worn some and not recently adjusted.

Mart's 1-1/16" E250 master cylinder is a good alternative; but is physically larger and will require a bulge in the floorboard cover. In my case I made a wood die and pressed a cover in my press.