Disc Brake Conversion

[Jessie J.]

One thing that isn't often mentioned about Studebaker's old original equipment Dunlop Disc Brakes, is that unlike most latter disc systems it is absolutely critical that the brake pads are regularly inspected and replaced.
The Dunlop calipers have cast in stops that prevent the metal backing on the pads from ever coming into contact with the rotor. If the disc pads are allowed to wear too thin they will come up against these stops. The Brake pedal will remain high and hard but there will be reduced or no front braking with no warning noises. I learned this the hard way at the cost of replacing the entire front clip on my ''65 Cruiser. The price of new set of rotors would have been much cheaper.
As a practical matter, unless your Studebaker is a full on restoration, that will be competing for points, there are much better, larger, (extended service life) and easier to service conversions available. The original disc system would be my last choice for anything I intended to drive regularly in modern traffic.

[Dick Steinkamp]

You can "Google" (Automotive disc brakes vs drum brakes) and get the engineers reasoning for discs being better overall. Has to do with the direction energy is used to stop a rotating object. I don't understand everything I know about the subject, but have used both and prefer the discs on all 4 corners if possible.

I googled those words. I get several "hits". I'm not sure which one you are referring to. The top one only talks about one difference...

"This basic design proved capable under most circumstances, but it had one major flaw. Under high braking conditions, like descending a steep hill with a heavy load or repeated high-speed slow downs, drum brakes would often fade and lose effectiveness."

https://www.edmunds.com/car-technolo...m-vs-disc.html

Do you have a link that would hopefully better define the term "better"?

What I don't get, is that if both systems on the same car/wheel/tire combo will generate enough braking force to slide the tires, what good is additional braking force?

[Alchemist]

If one were to install the whole disc brake system on a car which was not originally equipped, what proportional valve, (pressure modulating value), would be necessary to make the rear brakes operate in concert with the front discs?
Francis Prefontaine
Rolly View, Alberta

[thunderations]

This site probably goes into the most detail and compares drums to discs. (https://www.tribology.fink.rs/journa...6/2016-1/2.pdf) I will say that it looses me at times as I'm not an engineer and I really don't care about formulas and equations. Happy reading.

I googled those words. I get several "hits". I'm not sure which one you are referring to. The top one only talks about one difference...

"This basic design proved capable under most circumstances, but it had one major flaw. Under high braking conditions, like descending a steep hill with a heavy load or repeated high-speed slow downs, drum brakes would often fade and lose effectiveness."

https://www.edmunds.com/car-technology/brakes-drum-vs-disc.html

Do you have a link that would hopefully better define the term "better"?

What I don't get, is that if both systems on the same car/wheel/tire combo will generate enough braking force to slide the tires, what good is additional braking force?

[sals54]

If one were to install the whole disc brake system on a car which was not originally equipped, what proportional valve, (pressure modulating value), would be necessary to make the rear brakes operate in concert with the front discs?
Francis Prefontaine
Rolly View, Alberta

I did my disc brake conversion many decades ago. I did not use a proportioning valve on my sytem. I did, however experiment with different diameter wheel cylinders. I can't remember which one I ended up with, but it was fun going out, and at 50-60 mph, locking up the brakes to see when they would all skid together. Shade tree methodology, but it worked.
That was when I had more time than money to spend on my car.

[bensherb]

If one were to install the whole disc brake system on a car which was not originally equipped, what proportional valve, (pressure modulating value), would be necessary to make the rear brakes operate in concert with the front discs?
Francis Prefontaine
Rolly View, Alberta

An adjustable one. https://www.summitracing.com/parts/rsd-pv01 There are many available, this is just one of them.

I'm using the entire four wheel disk brake system from an '04 Mustang. It weighs the same as the C/K and has the same front to rear weight bias so even the proportioning is correct.

[chet445]

I had that valve on my '62 hawk using front disc and drums rear, did not notice any difference so just removed it. I must assume the rear rear drums are working as the car stops nicely. chet445

[Xcalibur]

Are there better brakes than the ancient Bendix/Dunlaps? Sure... but, that being said, there is nothing wrong with them, especially if on a reasonable weight vehicle.

For many years Jim Lange ran them on his Record Holding Bonneville Avanti and abused the poor things far worse than anyone ever would on the street. EVen so, they never did anything other than always bring the heavily ballasted car to a halt, including once when I was driving and the parachute failed. Man, did they stink, though, at the time... but, after allowed to cool worked fine the next day (as did the chute).

[Jessie J.]

As long as the pads are not worn thin ...when worn to the stops they quit working. No buzzing wear indicators, no dash warning lights, no metal on metal grinding. Just a stopping distance that unexpectedly becomes three or more times as long. BTDT. Mine gave out at a school crossing with 6 people onboard. Never again.

[64Avanti]

I googled those words. I get several "hits". I'm not sure which one you are referring to. The top one only talks about one difference...

"This basic design proved capable under most circumstances, but it had one major flaw. Under high braking conditions, like descending a steep hill with a heavy load or repeated high-speed slow downs, drum brakes would often fade and lose effectiveness."

https://www.edmunds.com/car-technolo...m-vs-disc.html

Do you have a link that would hopefully better define the term "better"?

What I don't get, is that if both systems on the same car/wheel/tire combo will generate enough braking force to slide the tires, what good is additional braking force?

Sliding the tires is not good for maximum braking. The drum brakes used on the front and rear of Studebakers without disc brakes are non linear. By that I mean the brake force is not proportional to the pedal force. The consequence is they are too easy to lockup. The disc brakes are linear and it is easier to control the braking at the limit to maximize the braking force and not slide.

[spokejr]

As long as the pads are not worn thin ...when worn to the stops they quit working. No buzzing wear indicators, no dash warning lights, no metal on metal grinding. Just a stopping distance that unexpectedly becomes three or more times as long. BTDT. Mine gave out at a school crossing with 6 people onboard. Never again.

What stops? The disc brakes I've worked on could still function (albeit poorly) with the backing material alone proceeding to destroy the rotor, just like a bonded brake shoe would destroy a drum.

[gordr]

If the piston is installed wrong, the stops won't work.

[48skyliner]

"What I don't get, is that if both systems on the same car/wheel/tire combo will generate enough braking force to slide the tires, what good is additional braking force?"

The important difference for me is that with bigger, more modern disc brake systems I have always had a much more comfortable pedal pressure to get the braking I want in any given situation, so I am not testing my strength in a panic stop. I have put large modern discs on several cars, but I always use the front and rear brakes from the same car, so balance has never been an issue.
My 48 Champion has the complete brake system , including booster and master cylinder, from a mid 90s Nissan, 12 inch discs front and rear, and it has really excellent braking. 17 inch wheels are required to clear the calipers.

[sals54]

The additional braking force is all about control. If your drums are fading with heavy use, its time to replace them with discs. I had 12" ventilated rotors on the front of my Coupe. Brakes from a 4500 lb car, used on a 3500 lb car makes for a non-fade brake experience.
Also, pumping brakes to come to a controlled stop is the way to go. I would MUCH rather have over sized disc brakes while pumping the pedal under an emergency stop. But that's just me.

[Jessie J.]

What stops? The disc brakes I've worked on could still function (albeit poorly) with the backing material alone proceeding to destroy the rotor, just like a bonded brake shoe would destroy a drum.

You have worked on disc brakes. Most of us with a considerable amount of auto repair experience have worked on disc brakes.
So the question is whether these disc brakes that you've worked on were the original equipment STUDEBAKER Bendix/Dunlop disc brakes with built in stops to prevent the metal backing on the pads from ever coming into contact with the rotor?
Not discussing any other make, or manner of disc brake caliper that you may have hands-on experience with.
I was pointing out that the 1962-'66 Studebaker disc brake design is rather unique among American built vehicles, in having these built in pad stops to save the rotors from being scored and ruined by worn out pads.
When the other American automobile manufactures introduced their disc brake designs they did not employ any such pad stops in their designs.

Of course if you regularly inspected and changed the Studebaker pads BEFORE they wore down to that point, you would perhaps never even become aware that such stops are present, even if you have replaced dozens of sets of pads. I had no idea of this 'feature' back in 1969 when my accident occurred. There were no warnings of such in the Owners Manual.

I cannot say with any certainty whether Studebaker ever eliminated this feature. But in 1969 when my disc braked '65 Cruiser piled into a line of stopped vehicles at a children's school crossing (crossing guard carrying a STOP sign, and a dozen or so little children in the middle of a busy 3 lane highway) The brake pedal was high and rock solid HARD, but there were no sounds, no grinding, no pulling. Just the horror of unexpectedly being unable to stop. The brake pedal actually bent under the pressure I was applying.
It was my STUDEBAKER dealer and Service Department that hauled my Cruiser in, and that brought this design feature to my attention, at the time of replacing the entire front clip ...and rebuilding the brakes. (the original rotors were still just fine) I was ticketed for "Failure to stop in clear assured distance."

Read the first paragraph;

http://www.studebaker-info.org/Tech/brakes/dunlop/dunlopreb/diskbrakes07.html

Another feature is, that the pads/pistons will only extend a fixed amount, preventing a pad from wearing down to the steel. A worn pad can never contact and gall the rotor. When the limit is reached, the braking effect diminishes. So, if the original Avanti disk brakes start to pull, they may be telling you to change the pads.

Don't depend upon hearing any grinding noises, or experiencing any unusual braking. Those pads need to be inspected and replaced LONG before they wear to the metal. (they never will)
A total loss of front braking power CAN occur during a single stop, and without any warning.

Anyone that operates a Studebaker with original factory equipment disc brakes NEEDS to know this!
Lives may depend on it.