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Has anyone updated the brake system from Treadlevac to a modern 2-chamber master cylinder? I did a complete brake job on my 53 Patrician, new wheel cylinders, shoes, hoses, plus a modern 2-chamber master cylinder, albeit, without a booster. Bled the brakes and, with great anticipation, took it for a spin. A very hard pedal, but No Brakes! Baffled, I have since learned a great deal about pedal ratio leverage and multiplication of force through hydraulics. Normal pedal ratio for a boosted brake system is 4:1. That is, 70 pounds force from your leg at the brake pedal is multiplied by leverage to 350 pounds at the master cylinder rod. The pedal ratio for the Patrician is an astounding 1:1! Thus, 70 pounds at the pedal is only 70 pounds at the mst cyl rod. It is no surprise that there is inadequate force to the brakes. Has anyone with a Patrician been through this exercise and come up with a configuration that works?

The short answer is no, at least nothing easy and nothing satisfactory. There is no modern dual master with the combination of small cylinder diameter and long stroke to match the treadle vac, and no way really to mount anything in the firewall. The only thing that really came close was a very elaborate hydrovac installation, which requires a power steering pump and a wholeot of other stuff, from the shop that created the Berendtsen transmission adapters. Other solutions get rid of the fresh air vent, and still have problems.

I know I have investigated a lot. Best just to rebuild the TV and perhaps use Dot 5 (some may differ on the latter point).

But feel free to search on this forum for "Treadle Vac conversion" Easamatic, dual master cylinder, etc.

A typical non-boosted brake uses a second class levered brake pedal. The Easamatic brake pedal has no lever action because your foot is pressing directly onto the master cylinder rod. To make your idea work you need to relocate the master cylinder and modify the pedal arm to achieve leverage.

Oh, and incidentally if the Treadle-Vac was relocated to achieve the same effect the result would be the world's touchiest system because that thing provides a lot of boost when it's working right.

Jerome, thank you for your very competent response. You're right, every option for changing the pedal configuration is problematic. The hydrovac, unfortunately, is beyond my competence. I considered an under-floor mounting to the frame, but the frame layout makes that impractical. For a firewall mount, there are cables, acclerator linkage and, as you pointed out, ventilation in the way.
Does the Treadlevac offer adequate braking? You mentioned its small bore and long stroke. Is that how the designers compensated for the 1:1 pedal ratio?

As Tim said, pedal ratio or location needs to change to get the modern systems to work satisfactorily. The reason the BTV works with the 1:1 ratio is it has an approx 3/4" diameter solid rod that moves thru the fluid and via the closed cylinder displaces the fluid and sends it out with greater force rather than what is possible with the modern masters 1" piston that pushes a volume of fluid ahead of it. I did some tests a few years ago and found there was almost a 2 times increase in pressure with the BTV. With no vacuum, 100 lbs pressure on the pedal resulted in almost 200 out and with vacuum, the same 100 lbs in increased output to almost 500.

There have been any number of conversions on V8 models but the only ones that have kept the new booster/master in the original location have had extensive pedal mods that raise the pedal higher off the floor and move it downward. This mod was developed by the late Craig Hendrickson in one of the first documented changes to a modern master. The relocated pedal is very noticeable but it does work. Moving the new booster/master up to the air vent hole has allowed a less drastic modification of the pedal or even using pedals from another car to get the proper ratio but still maintains almost the original look and position. Downside to that approach is you lose the drivers side air vent.

There are some interesting photos of the 56 that is in todays bring a trailer post. That setup is located high on the firewall -- almost to the top. It seems to clear the relays on the fender and it has what appears to be the original pedal but with a different mounting. Another poster has asked the new owner if he could take some more photos on that setup.

Tim, thanks for your input. I started this project rather naively. I just thought that if I mounted a master cylinder, it would work. The effect of the pedal leverage had not occurred to me. Now, with no leverage, a 1" diameter master cylinder does not work. I am surprised to hear that the tiny Treadlevac actually produces as much boost, as you say. After all, it is only about 6" in diameter! Are the brakes in fact adequate with the original setup? And how effective are the brakes in an emergency, if the engine stalls and you lose vacuum?

Howard, thanks for helping to make my options more clear. The test results you got on the TV unit are nothing short of amazing! Something is going on it that little unit that I don't understand. I now have a much better understanding of what I am facing, whatever option I choose.

The freshly rebuilt Treadle-Vac in my 1954 Patrician stops on a dime, so to speak! It’s almost too powerful but easy to get used to.

The TV piston has an area of only .44 square inches so a press on the pedal of 100 pounds yields almost 230 psi. A typical modern piston has an area of .88 and will yield only 113 psi. And of course the booster can add up to another, oh, 300 lbs pressure to the piston if you really stomp it yielding up to 800 psi brake line pressure.

My estimate is that Packard sold almost 150,000 cars with Treadlevac as it was a popular option. It was also installed on many other makes including Continental and Mercedes.

They work great with a very short pedal travel in normal driving. In an engine-fail emergency, they are no different than any other vacuum assisted power unit. You have to press hard. The only weak spot in the design is that they will not tolerate dirty lumpy brake fluid.

Yes; a couple successful conversion have been made. I actually purchased the components for one of the systems. The pedal will have to be moved lower and away to get the right ratio. However people say it was easy to get used to. I'll look around for the information I have and post it.

DOT 5? I tried it after a total rebuild of my brake system on the 56. It caused my brake switch to malfunction after 2 months.

BTV, a great system, I love it, however its a single system, it's only down fall

Dave O