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WRT whether drum brakes are adequate or not, everyone should be reminded that the late JR series Packard has 11in drums and the SR series has 12in drums. According to the 1955 Service Manual, the difference in effective area is 192in-sq (JR) vs 208in-sq (SR) or the JR is 8% less than the SR.

I experienced 100% brake fade on my Dad's 1955 Clipper (JR) in 1962 when trying to stop with a full load of high school kids on a long downhill. That is one of the reasons I installed front disc brakes on my 1955 Pat in 2000. I have never experienced brake fade with it.

Be that as it may, if the BTV fails, then discs vs drums do not matter, do they?

Craig

Are Jr and Sr brake drums and assoc parts a straight swap?
Were the larger brakes a HD option for Clippers, for trailering etc?

Quote:

I'm sure if you had a SR donor of the same year the swap would be no problem. 1955 and 1956 rear ends are different and hence the rear support plate assemblies are different and I don't know if they would interchange. You could always swap out the entire rear end though.

If you were going to that much trouble and have a 1956 rear end available, put on 4-wheel disc brakes. Rear disc brakes from the aftermarket are readily available because it is a Dana.

Craig

Several comments:

There is a post saying that driving through a thunderstorm with disc brakes is safer than with drum brakes. Consider the following. The danger in a thunderstorm is hydroplaning where the tire "rides" on top of the water like a hydroplane boat thus making safe braking impossible as it is necessary for the tire rubber to contact the pavement in order to brake. Teh typ[e of brakes is irrelevant in this case. What is more dangerous with drum brakes is to drive through a very deep puddle submerging the drums. Unless you pump the brakes to get the water out form inbetween the liknings ad drums yoiur braking will be dangerously compromised.. Disc brakes do not have that problem. I have not experienced this in 48 years of driving.

There is no argument that disc brakes are better, but for regular driving as encountered by most of us there is not much to be gained.

Brake fade in drum brakes is caused by excessive heat buildup and has to do withat least these factors.

First by the adequacy of the size of the brakes in relation to the loaded weight of the car. If you have 5 extra 200# buddies in your car it will fade sooner.

Next it has to do with the grade of the lining, Cheaper linings will fade more quickly, heavy duty will fade less

Last- brake cooling. Ventilated wheels that promote airflow through the wheels help cool the brakes. Finned drums should help dissipate more heat

BTV FAILURE DIAGNOSIS

A v-8 owner had a BTV rebuilt and it suffered sudden failure soon after. It was returned to the rebuilder who checked it, perhaps re-rebuilt it and returned it to the v8 owner. It suffered the same failure soon after.

This chain of events has occurred numerous times that have been reported on Packardinfo.com and the BTV is blamed for having an unsafe design. There are a significant number of members who advocate replacement of the BTV with a modern unit.

I made an arrangement with the V8 owner to purchase the unit for research. Here is what I found.

Photos to be attached when I figure out how (help appreciated)

See photo 2: Some type of silicone sealer has been used at the top of the lower counterbore. See curved sealer after washer was removed. Note, there is no seal needed at this point, none was used originally and its presence in the hydraulic system could lead to seal/valve failure.

See photo 1: Fluid return port plugged with silicone sealer.
This explains the failure, fluid cannot be returned to reservoir , when cavity between hydraulic rubber seal and \metal/leather seal fills up, it will be sucked into the vacuum section.. Eventually all the fluid is depleted and the brakes do not function.

It is clear to me that the rebuilder (not identified by V8 owner) is incompetent and does not understand how the unit works.

BAck in the 50's/'60's there were millions of BTV's on the road, rebuilders did hundreds of thousands of rebuilds and did them well. That would explain why there were few problems then and the above example explains why there are frightening problems now. Keep in mind that if a modern master cylinder is rebuilt by an incompetent rebuilder it may fail also.

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The rebuilder of that unit obviously did not know what he was doing. Thanks Fred.

fred -

Thanks for the "inside" info.

I can also envision a loose bit of that silicone sealer preventing the compensator port valve from sealing - as bad as chunks of dried up old brake fluid. Yet, imagine what would happen if one of those insoluble bits had migrated downstream.

Silicone sealer has its place in auto repair, but not here. Even if the counterbore of the body had required sleeving, there are more appropriate sealants available for that purpose.

Prior to disassembly and inspection, were you able to duplicate the failure of this unit on your tester? Will you now rebuild this unit with the parts that you sell and subject it to testing - both bench and on-car?

When we removed the reservoir cover and found the plugged port no testing was needed, the reason for the failure was obvious.

This unit will receive a new stainless piston as the old one had scratches running lengthwise. It had not damaged the rubber seal but we will replace it anyway.

This unit will have the silicone removed , will be rebuilt and tested then sold on an exchange basis.

I would like to buy/borrow ohter units that have experienced failure to do further research.

As someone who drives a BTV car, with family and particularly grandchildren... I really appreciate the work Fred is putting into this, I especially his persistence; most of us are not jewels towork with....