Brakes: Residual valve removal

[StudeNorm]

I tested my Lark with the newly installed Turner brakes and they felt smooth and balanced but they would not completely disengage and the back brakes were totally ineffective. Do I remove both residual valves as per the instuction at one site in Bob's Studebaker Resource page? I also read about an in-line residual valve being needed but I am thinking that might be for a under-the-floor M/C car.

Any thoughts? Thanks.

[BobPalma]

Norm, this question came up in an exchange I was just now preparing for the February 2015 Co-Operator on which I am working. I questioned Jim about it and here is his reply, as prepared to use in the column:

Jim Turner generally advises that a residual pressure check valve is used only when the master cylinder is below the level of the wheel cylinders and/or calipers.

BP

[64V-K7]

Do I remove both residual valves as per the instruction at one site in Bob's Studebaker Resource page?

That pictoral on my site is for a Turner Dual Master for a GT Hawk with disk brakes. The Factory Disk brake (single circuit) master cylinder had NO RPV (residual Pressure Valve) at all, but the rear brakes were not like yours. Larks have self energizing brakes, Hawks did not. If your master cylinder is on the firewall you don't need an RPV for the Disk Brakes as it will make them drag and overheat. However the Lark's rear drum circuit should have an RPV to maintain line pressure and keep the shoes closer to the drum, which will alleviate having to pump the brake to get a decent pedal.
So make sure
A) your front brake circuit is plumbed to the appropriate MC port,
B) If you haven't removed the RPV from either MC port, then only remove the one to the front circuit.

[BobPalma]

Thanks for that, Bob (Post #3). I am going to incorporate that in The Co-Operator as well. BP

[DEEPNHOCK]

Be careful when talking about residual check valves.
There are two sizes (psi ratings) for them. 3psi, and 10psi.
The 3psi residual check valves are for anti siphon used on low mounted master cylinders.
The higher 10 psi residual valves (which are either in-line, or built into a master cylinder), are used to keep a small pressure in the drum brake system to keep the shoes out close to the drums.

Read up on it...

http://www.mbmbrakeboosters.com/index.php?option=com_content&view=category&layout=blog&id=8&Itemid=16

http://www.classicperform.com/TechBook/BrakeTroubleshoot.htm

[StudeRich]

It is not that simple Jim and Bob P.

After carefully reading all of the above Posts especially Jim Turner's response to Bob Palma I would caution printing this unless it IS made perfectly Clear which Brake setup we are talking about.

Jim's statement works ONLY IF the Car happens to be a Drum Brake Car; '47-60 non-C/K or Lark or '53 to '64 C or K Model with the added Turner Front Discs. AND the Stock (non-Front Disc.) Rear Brakes with a Single Under the floor Master Cylinder.

If it is a Disc. Brake '63-'64 GT Hawk with the under the floor stock, single M/C it has NO Residual Valve or rubber seat and needs to stay that way, since changing to Turner Discs. changed NOTHING.

Jim Turner generally advises that a residual pressure check valve is used only when the master cylinder is below the level of the wheel cylinders and/or calipers. -I guess, HEAVY on the Generally!

[DEEPNHOCK]

Now Rich.....
You are screaming about the non stock sky falling again...So contrary you try to be.....

A Turner dual chamber master cylinder upgrade kit is a very worthwhile addition to a Studebaker.
Just know what your particular application is and make sure you have the correct parts there.
Jim has to say what he says because people make all sorts of changes to his products 'after' they buy them.
Sometimes people upgrade the master without changing the brakes from drum to disc.
Sometimes it is hard to make a single statement to cover all scenarios.

Adding a dual master cylinder to a '63/'64 GT Hawk is still a worthwhile investment in safety, because it is a dual system.
Please explain in great detail how this is 'NOTHING' (your words)

It is not that simple Jim and Bob P.

After carefully reading all of the above Posts especially Jim Turner's response to Bob Palma I would caution printing this unless it IS made perfectly Clear which Brake setup we are talking about.

Jim's statement works ONLY IF the Car happens to be a Drum Brake Car; '47-60 non-C/K or Lark or '53 to '64 C or K Model with the added Turner Front Discs. AND the Stock (non-Front Disc.) Rear Brakes with a Single Under the floor Master Cylinder.

If it is a Disc. Brake '63-'64 GT Hawk with the under the floor stock, single M/C it has NO Residual Valve or rubber seat and needs to stay that way, since changing to Turner Discs. changed NOTHING.

Jim Turner generally advises that a residual pressure check valve is used only when the master cylinder is below the level of the wheel cylinders and/or calipers. -I guess, HEAVY on the Generally!

[JoeHall]

I have installed 12" disc brakes, and Turner dual MC kit simultaneously, in three 56Js and one GT. I prefer a new NAPA MC (#36237), and have never removed the RPV from any of them, but not sure if they had one. I did, however, install an in-line 3 PSI front, and 10 PSI rear RPV on each car.

When pulling up to a stop sign on a slight incline, there is a very light drag on the front brakes, since the car does not roll with foot off the brake. But if its much of an incline at all, it will roll. I doubt it would even be present with the smaller Turner rotors & calipers.

In any case, I have ran those brakes, cumulatively, for at least 100,000 miles, and never had a problem. They do not heat up, nor wear out pads. I have replaced pads, but only to upgrade them, not because of wear.

Just my experience.

[StudeNorm]

All excellent replies. It seems the main theme here is knowing which application you need to be concerned with. Mine is a Lark type sedan with original drum brakes and firewall hung dual M/C.

I once owned a 1962 GT Hawk with disk brakes. The previous owner of that car not only installed the disk brakes out of a '63 Hawk, he also installed a firewall hung, single power M/C unit from a later model Lark. I changed the M/C to a dual unit I bought from Dave Thibeault back in 1988. He assured me it would work without modification and so it did. The car's brakes worked flawlessly for me other than having to change a leaking wheel cylinder at one point during my ownership.

As for this latest question... I will pull the front brake line and check for/remove the RPV from my non-original dual M/C. I have only had the car for a month so I am still learning things about it. I know it is a replacement M/C due to the adaptors used at the connectors. I expect it to have built-in RPV's. It sounds like I will need to leave the rear RPV intact.

I look forward to reading Bob's article in T/W.

[Aspalen]

For my Transtar -57.

With a remote fluid reservoir on firewall, and under floor master cylinder, and Turner disk brake kit.

Do I need the residual valve for the rear drums?

Disk brakes Gran Turismo have similar setup, with no residual valve.

[StudeRich]

Please explain in great detail how this is 'NOTHING' (your words)

This is an EASY one Jeff, you just took that out of context!

Quote: "If it is a Disc. Brake '63-'64 GT Hawk with the under the floor, stock, single M/C it has NO Residual Valve or rubber seat and needs to stay that way, since changing to Turner Discs. changed NOTHING."

So in the case I mentioned (quoted above) adding Turner Discs up front will be no different than the stock front disc./rear drum for disc. factory setup on '63-'64 GT's concerning the subject: Residual Valves.

And this is Bob P's J. Turner quote that does not apply to all:

"Jim Turner generally advises that a residual pressure check valve is used only when the master cylinder is below the level of the wheel cylinders and/or calipers." -I guess, HEAVY on the Generally!

You read into this something about Dual Master Cylinders, which I never mentioned.

[DEEPNHOCK]

OK... Got it.

This is an EASY one Jeff, you just took that out of context!

Quote: "If it is a Disc. Brake '63-'64 GT Hawk with the under the floor, stock, single M/C it has NO Residual Valve or rubber seat and needs to stay that way, since changing to Turner Discs. changed NOTHING."

So in the case I mentioned (quoted above) adding Turner Discs up front will be no different than the stock front disc./rear drum for disc. factory setup on '63-'64 GT's concerning the subject: Residual Valves.

And this is Bob P's J. Turner quote that does not apply to all:

"Jim Turner generally advises that a residual pressure check valve is used only when the master cylinder is below the level of the wheel cylinders and/or calipers." -I guess, HEAVY on the Generally!

You read into this something about Dual Master Cylinders, which I never mentioned.

[bezhawk]

If the car came from the factory with disc brakes, it doesn't matter if it is a Lark Hawk or Avanti.....all the rear brakes were identical on these cars. that is non self energizing.

[Warren Webb]

Correct me if I'm reading this wrong or not, but all cars equipped with Disc Brakes, both 63 through 66 used the same rear brakes. They were NOT self-energizing and did not require a RPV. Cars made with standard brakes were self-energizing so that if "those cars" are converted with disc brake fronts, then a RPV is required for the rear circuit, right? It would be plumbed into the existing brake line going to the rear brakes or would this be used only on "floor mounted" master cylinders?

Some of my comment here is repeating what others have already said but in some of the comments contain wrong or incomplete information. Some comments gave the impression that the brakes on Hawks & Larks are different when the opposite is true.

[bezhawk]

Cars with standard drum brakes still wouldn't need a residual pressure valve if it had the firewall mounted master cylinder. The under floor master cylinders did have them and they were attached to the piston return spring inside the master cylinder. Hawks had the hydrovac remote power booster and the master cylinder under the floor with the rpv.
Disc conversions with firewall master cylinders do not require a rpv, even if it was regular brakes to begin with.