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Andrew M

Re: Treadle Vac Conversion

#11

Quite a regular

Here are two master cylinders with 5/8" bore size according to Summit's website. They don't give any information about the stroke though.

My biggest concern with the way that ABS Power Brake makes their system is the fact that the brake pedal looks low to the floor when compared with the original brake pedal in relative location to the gas pedal. Craig's pedal was similar to how ABS does theirs, however, I haven't heard much feedback regarding this conversion that others have similarly done. Blocking off the air vent and putting it on the firewall is not really a good option for me since I live in a hot environment in the summer, unless I put aftermarket air on the car.

ABS mentioned that they were measuring the pedal ratio from the pivot point on the pedal to the center of the pad as well as where the bolt is through the pedal arm from the booster to the pivot point.

Links to 5/8 Master Cylinders:

https://www.summitracing.com/parts/ceb-130-45402

https://www.summitracing.com/parts/ado-18m1192

Posted on: 2022/2/5 23:25

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Andrew M

Re: Treadle Vac Conversion

#12

Quite a regular

Quote:

JeromeSolberg wrote:
That's an interesting find! It has a chance of working. The important thing (as noted by HH56 below) is what is the stroke? Might not know until you get one.

Question: The specs list two piston diameters 0.625 and 0.875. I don't quite know what that means, but that could be some kind of inner proportioning valve. Also, the specs could be inaccurate.

In a standard dual master cylinder, the primary piston pushes on the fluid only, and the fluid itself is what pushes on the second piston, unless there is a failure in the primary circuit.

How Stuff Works - Dual Master Cylinder

If it's anything like a standard-design dual master cylinder, the important spec is the diameter of the primary piston. If that's 0.625", then well worth a try. If it's 0.875", might not be. Also have to find a booster less than 7" diameter that would bolt up.

If you want to go ahead and try the 740 Volvo Cylinder, I would be willing to ship you my 7" Ford Courier Brake Booster, which I know fits in there on a 1953 and presumably also then a 1955/56, on the condition that if everything works well you would ship it back.

Those Ford Courier Brake Boosters are still somewhat available. What I saw for the Volvo 740 was 8" diameter, which wouldn't fit I am pretty sure.

1981/82 Ford Courier 7" Brake Booster #53-5211 (Autozone)

I called the company and found out that the initial rear of the master would be 5/8 and the front would be 7/8. They said it didn’t matter if the front or rear was attached to the 5/8, but one would be attached to the 7/8 bore. In other words, the 5/8 comes first before the 7/8 from what I understood.

Quote:

HH56 wrote:
Here are a couple of shots in mockup and in the car. As I mentioned, still a work in progress.

Is your master cylinder and booster in the stock location? Your set up looks nice.

Posted on: 2022/2/3 14:36

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Andrew M

Re: Treadle Vac Conversion

#13

Quite a regular

Thanks for the links. Here is another 5/8 bore dual master that is originally for a 1980’s Volvo. It is designed to be used with a booster. Would this be any better of an option? I couldn’t find what the stroke is on this one compared to the Treadle-Vac.

Link to Master Cylinder:

https://www.stockwiseauto.com/dorman-m39641-brake-master-cylinder?fit_id=6059&Year=1987&Make=Volvo&Model=740&gsID=pxf1974760f6059&gclid=EAIaIQobChMIzvyXvPHi9QIVj67ICh1Wlg2DEAQYAiABEgKylvD_BwE

Posted on: 2022/2/3 1:24

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Andrew M

Re: Treadle Vac Conversion

#14

Quite a regular

Quote:

JeromeSolberg wrote:

That way you can compare to what you would get with the original setup with an approximately 5/8" master cylinder diameter and a 1:1 pedal ratio.

Note - I have never measured the actual diameter of the T.V. piston (really a rod displacing fluid) myself, I have seen it as either 0.655 or 0.625 or even 0.62.

So for:

D = 5/8 and a P.R.=1, you have

Pressure/pound of foot force ~ 3.25

Hope this helps!

I spoke with the company and they think that it is a 15/16" bore master cylinder . He said that he would check on the pedal ratio and I will call back tomorrow. He thinks it is a 4:1, but I personally don't see how. I think a 3:1 would be pushing it looking at the picture.

Another option I thought of would be to use a 5/8 dual master cylinder with a remote mounted booster. I found a dual 5/8 master cylinder that looks to use one master cylinder for the front brakes and one for the rear. I also saw a regular dual remote master cylinder that is also a 5/8 bore. Would either of these work with the pedal in the factory location since the bore is similar to the Treadle-Vac? I would also add a booster to the system, but I want to be able to stop without it.

Links to 5/8 bore dual master cylinders:

Dual Master Cylinder Kit, 5/8″ bore

Tandem Master Cylinder 5/8" Bore

Posted on: 2022/2/2 22:55

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Andrew M

Re: Treadle Vac Conversion

#15

Quite a regular

I talked to ABS Power Brake and they said that the Oldsmobile setup in the original link would be similar, however, due to the frame on the Packard, they did not think it would work. They said that they actually have a system for the 55-56 Packard that they have put on several cars in the past. They sent me some pictures of their previous installments, and I think that I will probably go with this route. The technician I talked to said they would need me to send the floor plate that the Treadle-Vac attaches to, and they would install the parts and mail them back to me. He also said that the pedal linkage would be changed to compensate for a 5:1 ratio for the pedal. He also said that the pedal would be in about the same place as the factory once installed on the car. Here are some pictures of one of their previous installs on a 56 Packard. The booster is not straight because the bolts are loose for the install.

Attach file:

IMG_18571.png (826.57 KB)

IMG_18601.png (1,077.53 KB)

IMG_18451.png (923.16 KB)

Posted on: 2022/2/1 20:43

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Andrew M

Re: Treadle Vac Conversion

#16

Quite a regular

My Treadle-Vac works fine on my car, and I check the fluid every time I drive it. I’m just not a fan of the single master cylinder. I live in the mountains and we have lots of traffic here these days. I’d rather have something that I can rely on.

Posted on: 2022/1/31 8:10

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Andrew M

Re: Treadle Vac Conversion

#17

Quite a regular

I’m going to call the company tomorrow. If I can make it work, I think it will definitely be a good idea. On my 60 Chevy, I had to put shims under the bottom two bolts of the booster/master to tilt it up some, might could do the same on the Packard if it will fit.

Posted on: 2022/1/30 19:03

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Andrew M

Re: Treadle Vac Conversion

#18

Quite a regular

There is a picture of the linkage in the article. It is attached where the Treadle Vac attaches originally. The remote master cylinder then attaches to that. I think this may be the type system member “buddyfromvb” used on his car. I think ABS makes it. I’m going to call them tomorrow to see if they still make it.

Posted on: 2022/1/30 18:37

Topic | Forum

Andrew M

Treadle Vac Conversion

#19

Quite a regular

I have been researching on different options besides using the factory Treadle-Vac system on my 56 400. The main problem with converting to a modern type master/booster is the 1:1 pedal ratio. I do not want a master/booster on the firewall due to it not looking original. I want to keep it in the toe board area where it is from the factory. Last night while researching, I came across a product by the ABS Power Brake company in California. It mounts in the same holes as the factory Treadle-Vac and has an additional linkage to compensate for the 1:1 factory ratio to increase the ratio to a more modern 4:1 or so. The kit in the link below is installed on an Oldsmobile or Pontiac I think, however it is the same concept as the Packard. The kit they are using uses an electric booster, but if I have to use a remote booster, I would prefer a vacuum type. In the article they also convert to disc brakes, which I don't know if I will do or not, however the company offers a disc brake kit for the 56 Packard. Has anyone ever used this type setup, and would it work on my 56 400?

Here is the link to the article with the Treadle-Vac conversion.

Brake System Upgrade from Treadle Vac with ABS Power Brake Inc.

Posted on: 2022/1/30 17:31