Bob's Resource Website (2007)

Brake Systems on Studebakers

Note: I've been working on this paper for years and there's a lot of info to put in perspective. So, it's not finished, but is a good read to this point.
I'll be adding and reorganizing as time goes by../RJ

Studebaker Brakes (1953-1964)(General)
     Master Cylinder (MC)
The one standard to most all Studebaker brake systems is the 1Ē bore MC, which was mounted on the frame below the driverís feet and has a one inch bore. These MC's are used on all brake systems in C/K type vehicles and many other models. The internals, in order of usage, consisted of a dust boot, covering the single piston, a spring and a residual pressure valve (RPV). An explanation of the importance of the RPV, is below. The 1" MC was the standard on many years and models, the only variation, being on the disk braked GT Hawks. On this application, there was no residual pressure valve installed on the piston return spring.  


  The Anti-creep option was a brake holding feature used on cars with an automatic transmission. It consists of an electric pressure switch, mounted on the rear of the transmission, a solenoid in the brake line, a paddle switch on the throttle linkage. When the brakes were applied and stopped the car, the pressure switch was closed through low transmission line pressure. The switch, then provides current to the brake line solenoid and locks the line pressure. The vehicle was held in place and you could actually remove your foot from the brake pedal. When the accelerator was pressed, a paddle on the throttle bell crank, moved away from a pin switch, opening the ground of the the solenoid, releasing the brake line pressure and allowed the car to move again. Anti-Creep was only configured to operate on the rear wheels and used a dual outlet at the Master cylinder. Anti creep switches could be ordered in 6 or 12 volt and were used as accessories up to 1964 (66?).  

The NO-Rol or hill-holder is a device that locks the brake line pressure, using the action of the clutch linkage and is a simple ball check valve. The brake line pressure is released when the clutch pedal is raised. The No-Rol unit is configured to operate on both front and rear wheels and the action is entirely mechanical. The unit has to be separately bled as part of the routine brake maintenance. 


     Power brakes
Studebaker Power Brakes were introduced in 1955 and used the Bendix Hydrovac. This is a remotely mountable, power boost system, which multiplied dynamic input line pressure from the brake pedal, through a vacuum/diaphragm/plunger mechanism and was successfully used by many car manufacturers for years, including Cadillac, Mercedes and Ferrari. You can mount the Hydrovac anywhere on the vehicle and connect the input/output brake lines. The one downside to using this type of booster is that itís designed for only a single circuit brake system. The Hydrovac was used by various Studebaker models, until 1964. They differ in applications pertaining to trucks and there are differences in car applications also, such as the power drum brake unit (type A), as opposed to the disk/drum brake hydrovac (type F). Compare the two types. The main difference between the two is, the type "F" has a smaller diameter power piston and the power piston has different internals. Versions of the Hydrovac are still used on large trucks and variations have been developed over the years, which are still in use, today.

Along with the Hydrovac, Studebaker introduced a new power brake pedal. Functionally, the pedal had a much shorter stroke (see inset) and came to be called the 55% pedal. The power brake option was a welcome improvement, to the ladies, as they didn't have to lift their legs, too high, to apply the brakes. With a ratio of ~4:1, versus the ~7.5:1 ratio of the standard pedal, the mechanical advantage of the new pedal was significantly less than the mechanical one. In a power brake system, if your Hydrovac fails, stopping the car will require a great deal of pedal pressure.

At the factory, the installation of power brakes required that a new pivot point be bolted to the frame, approximately 4 inches in front of the standard pedal pivot. The power brake pivot was necessary to accomodate the shorter pedal length, and resulted in the requirement for a longer actuator rod than the standard brake application. The standard pivot point was still used for the clutch linkage, in a manual transmission car. The standard brake/clutch pivot was always welded in place when the chassis was manufactured, so all power brake application cars, still have the standard pivot welded to the frame. On power brake cars, the standard pedal pivot became part of the MC brace.

Studebaker used Hydrovacs through 1964, but introduced a suspended brake pedal in the 1962 Larks. The 62 Lark used a standard firewall mounted booster and single circuit master cylinder.

From 1963 through 1966, a dual circuit master cylinder was used for drum braked sedans. It could be supplemented with a power booster mounted on the firewall.

With the introduction of disk brakes in 1963, sedans and the Avanti, used the same single circuit master cylinder and booster.

    NOTE: It's fairly easy to change a firewall mounted single circuit master cylinder to a dual circuit type.

The boosters for disk brake sedans and drum brake sedans are different. For the 56-61 C/K's and GT Hawks, the ONLY combination used was the underfloor master cylinder and the Hydrovac. The Hydrovac for a Disk braked GT Hawk is a different unit than the one used on any drum braked car.

     Master Cylinder Vent caps
The Master cylinder cap on most single circuit Studebaker MC's is a direct screw-in type with a small hole for a vent and uses either a composition or copper sealing washer. The vent hole is a poor design feature, as it allows moisture to come in contact with the brake fluid, which is highly hygroscopic (will absorb moisture). The fluid level drops as the friction surfaces wear and more fluid is required to move them closer to the rotating components, as they are adjusted through their lifespan. As fluid drops, moisture is drawn in with atmosheric pressure.
It is always advisable to change brake fluid in a Studebaker every two years, as this moisture will eventually saturate the fluid. Once past the the saturation point, it will remain as water, accumulating in a low spot, to eventually rust through the line or pit the wheel cylinders. If you compare the caps with type newer master cylinders, you can see a rubber, diaphragm, cap gasket. The cap gasket will deform as the fluid drops to keep the container sealed and moisture out of the fluid.


   Studebaker brake lines are generally 3/16, I.D. steel and travel from the MC to either a No-Rol/Anti-creep, or forward to a distributor block, at the main cross member, which tee's off to separate steel lines to a junction at each spindle, then to a flex line, and then to the wheel cylinders for the front brakes. The distributor block also contains a brake light switch and generally a line, along the inside of the frame to the rear wheel arch, down a rubber flex line to a distributor block on the rear axle and then steel lines to the individual rear wheel cylinders.

On later cars with disk brakes, a remote brake fluid reservoir is mounted on the passenger side of the firewall. This reservoir was connected to the master cylinder, using standard steel/brass plumbing and connected to a special master cylinder cap. The cap on the remote reservoir was still vented to allow fluid drop and still has the deficiencies, noted above.

   Residual Pressure Valve
In the Studebaker underfloor Master Cylinder, the RPV is a small tin hat with holes and a rubber diaphragm, on the output end of the spring.( see insets)This valve serves two purposes. When the brakes are released, the return springs on the shoes, having a calibrated pressure, pull the shoes off the rotating component. As the springs retract, fluid is forced back toward the MC, under pressure from the springs. As the spring relaxes, the line pressure diminishes. At approximately 10#, the RPV in the MC stops any further retraction, resulting in approximately 10# of brake line pressure, after the pedal is released. This line pressure maintenance keeps the return springs from fully retracting, in order to keep more fluid in the cylinder. This prevents the MC from having to push a full volume of fluid out, next time, to engage the brakes. Also, in the case of an underfloor MC, prevent the weight of the fluid draining back to the master cylinder reservoir, where in the case of the Studebaker type, would overflow through the vent hole.
In a case where fluid drained back, the next time the brakes were applied, the pedal would have to be pumped up to fill the lines.

Disk Brake cars:

(edited June 2008)
Studebaker GT Hawk FACTORY Disk (Dunlop) brake front/drum rear - All factory C/K disk brake equipped cars used the same 1Ē bore master cylinder, but it had slightly different internals than standard drum brake MC's AND has a different part number. The Stude MC for the 63-64 disk brake Hawks is part #1558124 and the non-D.B. Hawks is part #531510. The difference is that the Disk brake MC has NO internal residual pressure valving (RPV). You can see this in the 59-64 Chassis manual and there's also a table of parts, used across the different MC's.
On the firewall of a Disk Brake hawk, is a remote brake fluid reservoir, which connects to a special cap on the master cylinder. The cap only has a threaded female flare connection for the reservoir supply tube and NO VENT. The Disk brake cars, also, used a special Hydrovac as standard equipment.

After the original disk brake Hydrovac application was on the market, a service bulletin was issued and a retro-fit kit, part #1565515, was installed in cars, whose owners complained about inadequate stopping power. The kit enhanced the power assist of the Hydrovac. The original application would seem to run out of boost when you were almost stopped and the kit remedied this, by increasing the line pressure to ~900-1000 psi (wf:1)
The part number for the D.B. Hydrovac, used on 63/64 Hawks, is 1558380, Type F. The 63/64 Drum power brake cars part # is 1544394, Type A.

Due to the non-self energizing action of both the rear drum and disk brakes, a disk braked car would, typically, need 900-1000 psi brake line pressure at the wheels. The Disk Brake Hydrovac (1558380) has a significantly smaller snout and power piston, at around .75", than does the drum brake unit (1544394), having a 1" piston. Another different feature of the two units are that the Drum brake unit has two bleeder fittings, the disk brake unit only has one, on top of the unit. The Disk Brake Hydrovac unit repair kit is number #1559734, the Drum brake unit is #1541846
You can use a drum brake Hydrovac on a Disk Brake car, however the boost is significantly less.

The rear drum brakes on a Disk Brake Studebaker are "servo, non-self energizing" and were used to counter the requirement for a proportioning valve. A self-energizing brake, upon application, will 'wind-up' inside the drum and increase the stopping power significantly moreso than the non self-energizing - Notes on
Rear brake shoe orientation on DB Cars

Oddly enough, there is no residual pressure valve in the MC either, to compensate for return spring pressure and there's no check valve in the Hydrovac for this purpose. The rear drum adjustment, using the locking eccentric, must have precise enough characteristics, that forego a requirement for it.

Stude Hawk (Factory) Disk brakes never used an RPV on the front for two reasons. Least of them is the Dunlop disk brake design, which incorporates a
pad retraction mechanism
. The retraction mechanism maintains a standard gap between the pad and rotor, when the brakes are released. On modern (Turner style) disk brakes, If the MC is below the calipers, a residual pressure valve is required to keep the pads close to the rotor. If the MC is below the height of the wheel cylinder, then drainback and overflow of the brake fluid is possible. The Factory disk brakes did not have any RPV's and the reservoir was on the firewall which supplied a sealed Master cylinder. More on this operation below.

The height of the brake fluid in the Stude Disk Brake MC reservoir, on the firewall, keeps some positive pressure in the brake line. If you swap a factory disk brake system for a Turner, some cases will require a 2# RPV. The rear drums should always use an RPV if they are self energizing, since it would help keep the shoes closer to the drums and prevent a low pedal on initial application.

Turner GM style disk brakes, as all modern types, have no mechanical pad retraction mechanism. What is designed into the piston is a seal that will deform as the piston moves with the application of the brake pedal. When the pedal is released, the seal returns to shape and helps pull the piston back. Not that this is a disparaging point, but the GM & other floating caliper designs only allow the piston seal to deform against the cylinder wall on application. When the brakes are released, the seal straightens, inducing a bit of clearance, along with releasing pressure on the piston/pad. That, plus the slight amount of wheel bearing wobble, is what allows free rotor movement. Over time, the seal will wear down and not retract as well, causing the pad to drag on the rotor.

Here's where the residual pressure valve sausage is made.... If you have a drum braked car and you change to the Turner system, your dual MC may have RPV's in the port(s). You have to remove the RPV from the port serving the disk brakes. If you have a Stude Factory disk brake car with a firewall MC (Lark/ Avanti) then your single MC should be adequate, as is. If you change to a dual MC then check the DB port for an RPV and remove it, if found. The factory rear brakes for a Disk brake car can be used with Turner system but may require an RPV. Try it without one and see if your pedal remains high

Whether or not, you use the original single Stude single MC or a dual aftermarket MC...

    The RPV's used by Turner are for cars with the MC below the floor, to keep the fluid from draining back and requiring a long pedal stroke to get braking. The one MC mainly recommended for Turners Frame-mount dual MC system is the NAPA 36237 and has evolved through a lot of applications. Since the evolution never included Studebaker, you have to tweak it for your application by removing the internal valves and later, installing the Turner (Wilwood) units), in the brake lines. Here's a Webpage to show how.
    If you do it like this, and have a reservoir on the firewall, you'll never, again, have to fool with getting under the floor to check fluid.

    Studebaker drum brake, single, master cylinders have a residual pressure valve, located on the front of the MC piston spring. This valve keeps approximately 10# or more of line pressure on the brake lines, after the pedal is released, to prevent fluid draining back to the master cylinder, under the floor.

    In a case where fluid drained back, the next time the brakes were applied, the pedal would have to be pumped up to fill the lines. Residual pressure valves are manufactured for specific results, according to brake components, return spring pressures, etc, so no one application really fits another.

    In the 63-64, drum brake Lark/Daytona cars, with a firewall mounted DUAL MC, there ARE residual pressure valves in each port, where you attach the brake lines.

    In the 62 drum braked lark, with a firewall mounted, single master cylinder type, there is a residual pressure valve on the end of the piston assembly.

    If you change a 63-64 Lark/Daytona, to a Turner front Disk brake setup, you HAVE to remove the residual valve in the line to the front brakes, whether you use a stock master cylinder or change to a larger reservoir type. The line to the rear brakes should retain the stock RPV or use the inline Wilwood 10# RPV, supplied by Turner. Drum brakes need an RPV, whether or not the MC is below the floor.
    Since the fluid reservoir for a Disk brake master cylinder is mounted on the firewall, the MC's do not need a residual valve. The tendency for gravity to keep the fluid dropping, maintains around 2-3# of pressure on the lines.

TURNER Dual Master Cylinder Bracket

Installing a Turner Dual Master Cylinder Bracket (left) allows you to replace the Studebaker single circuit master cylinder with an, up to date, dual circuit, master cylinder, which goes al long way toward improving safety in your car.
In a dual circuit system, if either one of the circuits get damaged, you can manage a safe stop using the other circuit.
Installation instructions come with a list of recommended master cylinders, to use on the bracket. Others have been found, with nice features, including remote fill capabilities. The things you have to remember, is that
1) these recommended master cylinders were used on applications other than Studebaker, so they have to be modified.
2) none of them were designed to be installed under the floor, of a Studebaker, so there may be issues that were not found initially. One of these issues involves the filler cap on some MC's, others involve the MC contacting a body brace, or crossmember.

The one item that is a sore spot and never understood, are residual valves. These are small rubber check valves, installed on ALL drum brake systems to maintain a certain level of fluid pressure in the brake lines. Turner's kit comes with Wilwood Residual Pressure valves. Depending on your application, you have to install a 10# valve on the lines to drum brakes and a 2# valve on lines to Disk brakes.
To modify ANY master cylinder, you have to open the unit and inspect if there are small rubber valves mounted in the line ports. If there are, they HAVE TO BE REMOVED and the unit reassembled with out them.

Here is a web page that describes how to accomplish the removal of residual valves ----->


After you have modified the master cylinder, you have to "Bench Bleed" it, before installing it on the car. This entails placing it in a vice and connecting the line ports to the reservoir, then slowly pumping the unit with a blunt tool to emulate the brake pedal action. This will replace all the air in the unit with brake fluid, prior to installation and helps greatly in getting the brake lines bled on the car.

Install the unit and then, plumb the NEW (Turner) residual valves as close to the master cylinder as possible.
Remember, even if you have a remote reservoir, above the master cylinder, AND front disk brakes, it's a good idea to install a front RPV.
However, no matter what, you DO NEED to install a 10# RPV for any Drum Brake setup.
To facilitate your new master cylinder and residual valve installations, you can purchase small lengths of, easily bendable brake line and unions, at your local parts store. It will look very professional and sanitary when you're done.

Variations on the theme
   You have drum/drum brakes and want to improve things..............
The first thing you should do, is inspect your components, to see if you have a power brake pedal, and if so, swap it out for a standard pedal. No other ONE thing will assure you more safety than that long pedal.
  Hydrovacs work satisfactorily when they are in good shape and maintained well, or if they have been rebuilt by a reputable shop. To those of you who swear by a Hydrovac, I won't argue your position, but for 45 years, my observation, is that "I've never met a Hydrovac that I liked".
It has often been stated that you do not need a hydrovac to have good brakes. You certainly cannot have good brakes if you have a marginal Hydrovac and/or a power brake pedal.
If you install a dual circuit master cylinder, the Hydrovac can only feed one of the circuits, since it's only designed for one.

  You can also install a Turner dual Master cylinder Kit and upgrade to a late model dual circuit master cylinder. If you install a dual master cylinder and want to keep your Hydrovac, another possibility is the use of a combination valve. Combination valves are designed to balance your brake line effort and meter pressure. The nice thing about these is the fact that they allow your rear wheels to start braking first, then allow the front lines to apply. This creates a very smooth stop, with no nosedive, especially in a panic situation.
The plumbing solution here would be to run the front and rear lines from the dual MC to the Combo valve ports, then out to the Hydrovac for the front brakes and an unassisted line to the rear wheels. The front brakes do 60-70% of the braking and they can use the Hydro assist more than the rears.

Bendix Disk brakes ( Excerpts from the 1961 SAE Paper presented by Studebaker)
Avanti Disk Brakes


Disk Brake
Turner Disk Brake (DB) Kits are designed to enhance the braking ability of your Studebaker, as well as introduce components that are readily available and very affordable. Changing the brake system requires an understanding of some standard components, particularly, the cylinder sizes, mechanical function and residual valves in the master cylinders. Included in the Turner disk brake (TDBS) kit, are 2 new residual valves, one red (10#), the other blue(2#).

If you elect to remain with the standard Studebaker single master cylinder you must, first, disassemble it and remove the residual pressure valve (RPV) from the front of the piston assembly. This is a good time to rebuild the unit anyway. The RPV is the small tin hat, with the rubber cover, at the front.

If you elect to upgrade to a dual master cylinder, you need to remove and discard the internal residual valve from the Dual MC unit, you choose, and install the supplied red and blue valves in the brake lines, to the specific wheels. There are exceptions to the front RPV as stated above.

    If you ignore the residual valves in the new unit, the combination of both residual valves will exert too much pressure on the brake cylinders and your brakes will start to drag, getting worse as they get hotter, until they finally lock up. You only need around 2# (blue) of line pressure on a disk brake application(Note:2) and 10# (red) on the rear drums.

    The Turner DB kit can be used on either a drum/drum car or a disk/drum car. There are differences in applications though..

    The Turner DB kit can be used with or without power brakes.


1970 Avanti - Four wheel Disk Brakes

Rear Disk Brakes


(020705)Turner DBS with a Hydrovac
Various opinions on this, due to the difference in supplied line pressure. The resolution would be to balance the line pressure in both the front and rear, using a combo valve.
To install a Turner (Disk Brake Kit) (dual MC) on a Disk brake car with the Hydrovac power boost - Use an 11" standard pedal only. Don''t even think about using a short (early) PB pedal, as Disk brakes require much more force than the early PB pedal will offer, plus the factory disk brake option included NON-self energizing rear drum brakes, which alleviates the requirement for a proportioning valve.

Fluid reservoir is in a remote tank on firewall, dual MC front fluid line routed to Hydrovac, (then to a 2# residual valve (See NOTE *1)), then to front wheel cylinders - rear MC fluid line routes to 10# residual valve, then to rear Wheel cylinders. Brake light switch can be at Hydrovac or tee'd inline if new lines are run.

Avanti Disk brake to Turner Disk brake (MC above the wheel cylinders)
Master Cylinder - 63-70 Avanti (4-bolt Replacement, dual circuit - mid 70's Chrysler. NAPA #36307.

Turning Wheels, April 2001 (Jim Turner , Jan 2003)
Master cylinder is from a 77 Chrysler. The NAPA/United 36307(cross references to Bendix 11515) no check valves, and no proportioning valve, as the Chrysler M/C is the same bore, and is ABOVE the wheel cylinders and calipers.
In this type of installation, the Turner DBS does not require the use of the blue and red residual pressure valves.

Original Drum/Drum system to rear drum with Turner DBS (MC above the wheel cylinders)62-63-64-65-66 Lark types
Master Cylinder - (four bolt type as above)
Master cylinder is from a 77 Chrysler. The NAPA/United 36307(cross references to Bendix 11515) no check valves, and no proportioning valve, as the Chrysler M/C is the same bore, and is ABOVE the wheel cylinders and calipers.
In ANY type of drum brake application, the Turner DBS does require the use of the 10# residual pressure valves on the rear brake line, no matter where your master cylinder reservoir is.

C/K type cars 53-64
Original Drum/Drum system or factory Dunlop Disk brakes, TO rear drum WITH a Turner DBS (MC BELOW the wheel cylinders)C/K types
Use standard Studebaker Master cylinder, but remove residual valve inside. Install Turner RPV's as supplied, 2# to front line, 10# to rear line OR

    Install a Turner dual MC Bracket AND Napa 36237/NAPA TS10-1854/NAPA TS10-1525
    Remove residual valve inside. Install Turner RPV's as supplied, 2# to front line, 10# to rear line (note - hydrovac may or may not be used

Note 1)
)On NON self-energizing brakes, the long shoe goes to the front.
)On self energizing brakes, the long shoe goes to the rear.
)To clarify: NON self energizing has a fixed shoe anchor at the bottom and each shoe has its own adjuster = long shoe to front.
)Self energizing has a star wheel adjuster and the shoes float around that adjuster = long shoe to the rear.

GM rear Disks
When upgrading from a drum rear, it is said the 82-89 rear discs require the J65 (4 wheel disk) master cylinder. Up until '90, GM used (2) master cylinders, including 1LE. - the J65 for disc/disc cars and the J50 for disc/drum AND 1LE. Starting in 1990, GM dropped the J65 MC and strictly used the J50 in ALL F-bodies - disc/disc and disc/drum.

The J65 Master cylinder was designed with a low pedal ratio for reduced free travel and a firmer and higher effort pedal for the high performance buyer. There was a GM bulletin (Bulletin # 84-88; Section 5 (V); Date: March 1984) stating that people hated the feel of the J65 brakes so they made available the J50 Master cylinder as a replacement. So in pre 1990, when GM customers used to come in and complain about their J65 disk/disk brakes...GM would actually swap on the J50 disc/drum master cylinder. (the one that was on my car) In 1990, the J50 became standard equipment for the disc/drum and disk/disk cars.

It is recommended to find an 89-92 disc rear. Those are the best, and you can re-use your existing J50 (disk/drum) master cylinder. Grab the prop valve too. GM still sells 'em for $80.


NOTE:2 )Even if you have a remote reservoir, above the master cylinder, AND front disk brakes, you will need a front RPV. wf:1 - Wayne Flowers ( Albuquerque, NM