Packard Forum Index » V-8 (1955-56)

The first 56 Packard (400) I owned was a good daily driver, BUT it took some getting used to the very sensitive power brakes. The person who sold me the car warned me about the brakes and within a few blocks I was well aware of just how sensitive they were. My 54 Patrician was not nearly that touchy, but I warned my wife the first time she drove the 400 (with me in the passenger seat) that the brakes were very touchy. She tested that after about 50 feet and almost put me in the windshield. My question is why are the brakes on my current 56 400 (Best Other)not nearly as sensitive? Perhaps Ross or some other mechanic can chime in and explain it. Are you other owners of V8 Packards aware or are your brakes not touchy at all? I do have asbestos (original) lining on the front.

That is an interesting question and hopefully someone has a good answer. One thing the BTV didn't have a lot of was pedal travel so anything that happens happens fast. Here is a 53 commercial demonstrating the very small pedal "tip toe" movement between no brakes and a full stop.youtube.com/watch?v=eMgriMYCtNc

One thing I could theorize is the BTVs we used rely on springs and a large rubber diaphragm in the power piston to provide some feedback for pedal feel and how the poppet valves are worked. If the rubber diaphragm has hardened or poppet valves are not seating as tightly perhaps there is enough change that the vacuum is not applied to the power piston as abruptly as it was when new and the response is slower.

Apparently the sensitivity was even an issue new because Bendix developed a hydraulic reaction BTV as a version after the one we used. Instead of the rubber diaphragm and springs sensing vacuum application to provide the feedback, it has a rod mechanism thru the ram which directly feels hydraulic pressure and provides feedback to the power valving.

Have not tried this yet for my 52, but in talking with a Packard friend, check the rear brake linings, if an axle seal leaked and grease got embedded in the brake linings might cause an overly sensitive brake.

It was not considered a problem. I am not looking for some fault like grease, badly adjusted shoes, etc.
The power brakes acted that way on ALL 56 Packards and I am assuming 55's also.
I would like to know why mine do NOT act in that manner.

The power brakes( and steering) of cars from the 1950's were just that....power. There was no road feel that we are used to with newer rack and pinion steering.....and slamming the brakes or even applying normal pressure can launch you.
I have a 57 Lincoln with BTV and 55 Cadillac with Hydrovac in addition to the 55 Packard with BTV.
Going from a new car and driving any of them takes some care since when the brakes are in proper adjustment they will all " grab"
I think the comments by the other posters are probably your answer. If the BTV is properly functioning, the shoes matched, the drums new or properly turned and the brakes properly adjusted....the Packard should grab with little peddle movement. If it is not doing that, I would change the rear pads, adjust the brakes and see if that returns you to the " sensitive" brakes you had on your prior car.
I am still a bit paranoid about the BTV based on the horror stories posted and prior failures that I have experienced with the Hydrovac and BTV
Units on other cars. I have had wheel cylinder failure with new cylinders, sucking of fluid from the master cylinder of the Cadillac with a recently rebuilt Hydrovac and most recently loss of the normal braking function on the BTV fitted Lincoln when forced into extended stop and go traffic when outside temps approached 90 degrees. The brakes worked fine until the car began to get too hot and the brakes used too often. The pedal seemed to need a pump to get proper feel and was really sensitive if you were forced to hit the brakes to avoid pedestrian and people making sudden stops.
This is all primitive technology and since there seems to be no simple way to keep normal pedal location and replace the BTV on the Packard due to the underfloor location and 1/1 pedal ratio....you just accept the situation and adjust driving accordingly....and pray.

From the "1953 Cavalier Road Test" that has been uploaded to this site, from a period publication:

"Power brakes are a bargain at $39.45 and they do almost as much to ease the driver's task. Vacuum-operated and very light, they tend to batter passengers senseless until the driver gets used to just feathering them."