Brakes - Wives Tales & Misconceptions

[58Yeoman]

Hahahaha
this is funny,....
I still stick with a single master and my trusty factory brakes.

I've always thought this, also. My '58 Chevy has a single MC and drums all around. So did my '63 Galaxie. I always figured the OEM engineers knew what they were doing.

UNTIL my 1988 Chevy K1500 PU. I bought it used in '89 with 15k miles on it, and the brakes just never felt right. I checked or changed everything I could to get them to work right. I finally went to the Chevy dealer where I had once worked and got to talking with one of the top mechanics. He told me that Chevy had a recall on the MC booster...they were too small. It was Chevy's fault, and it still cost me a hundred bucks.

 

[rich b]

Let me try to make this clear as I know it is confusing.

A PRESSURE DIFFERENTIAL VALVE will not nor was designed to block flow from a sound failed circuit (a circuit being either front or rear brake system deriving from the use of a dual circuit/reservoir MC).

That's what I felt I knew; guess I misunderstood part of your first post discussing the brake company's wording.

Now if people can be made to understand how a dual master functions and the need to design for full pedal travel if they are to gain any "safety" by the installation of one.

 

[KULTULZ]

As far as the '67 MC, I don't think it would have worked, KULTULZ. I have a set of valve covers on the engine that I really like (Ansen) - first of all they seal nice (which I could never get my originals to do) and I also really like the way they look. The problem with them is they won't fit with the original size booster. Only a smaller booster will have the clearance. Believe me, I tried. They aren't the high ceiling valve covers, either, but the lowest that Ansen has for my application.

I didn't realize the engine had aftermarket rocker covers.

The other common clearance problem with 4th gen T-Bird dual reservoir conversions is the under hood brace. The brace on the MC side is slightly different to clear the relatively short factory MC, but longer dual reservoir MC's typically still don't fit and it's common for T-Bird owners to go on a quest for something will fit...or it's common to cut a notch out of the driver side brace, which I definitely won't do. The other thing people do is buy modified braces. I don't know who makes them or if they're a cottage industry, but I know they have them for '66's, and maybe '64-5 too.

I'm going only off of memory, but I'm pretty sure the '67 MC won't fit without modding the brace. It's been covered at length on the VTCI forum, but please, anyone correct me if I'm wrong. Don't want to spread rumors or myths.

And I forgot about this (apron brace) on the BIRD. That is my fault.

I had to look a fair bit to find something that would fit the setup I have. I read decent reviews on the ABS products, but I'm not trying to make the case that this kit is the premium or optimum set up out there. Like I said, I didn't feel at all comfortable trying to engineer something myself.

However, I definitely will call ABS and ask them about the PDV and pressure residual valve function that may or may not be in my kit.

OK, I understand now as to cause a DUAL RESERVOIR to fit without modifying the brace, a smaller booster was also used. Now it makes perfect sense to me.

What I do not agree with is their use of a SPIN FOR DOLLARS ANTI-BIAS VALVE. The things are dangerous for a street car .

 

[KULTULZ]

That's what I felt I knew; guess I misunderstood part of your first post discussing the brake company's wording.

Again, that is my fault. I should have quoted their description fully and then made my snide remarks. I am getting old and go into b!tch mode WAY TOO EASILY (and I have been retaining water lately).

Now if people can be made to understand how a dual master functions and the need to design for full pedal travel if they are to gain any "safety" by the installation of one.

You are correct again. The true safety factor is within the MC design, not the PDV.

 

[KULTULZ]

Here (IMO) is a good tutorial on MC operation. Mind you that a much later style is being discussed but the dynamics are the same.

So grab a cold adult malt beverage and some snicky-snacks and peruse -

https://www.youtube.com/watch?v=Be4wNFSvxLc

 

[KULTULZ]

Proportioning Valve Selection

Selecting the correct adjustable proportioning valve for your vehicle entails not only selecting the proper point at which slope limiting begins (the kneepoint), but also selecting the proper rate at which rear brake line pressure builds after that point (the slope).

Nearly every adjustable proportioning valve on the market today has an adjustable knee point (the point at which the rear brake line pressure begins to be controlled), but a fixed slope (the rate at which it builds beyond the knee point). While one parameter is adjustable, both are critical to system performance.

SOURCE - CENTRIC - https://centricparts.com/getmedia/d...f-bf7e4451801b/brake-proportioning-valves.pdf

 

[JimNNN]

BTW, what's the opinion (if any) on bleeding the proportioning valve during installation? I bench bled the master cylinder for my car and when it was installed I hooked up the lines to the proportioning valve and bled those components (with clear hoses back to the MC.) I don't think I read to do that in the manual or anywhere else, but it seemed like a good idea. Maybe it wasn't. Of course once I got all the other lines hooked up, I bled the whole system. Is bleeding the proportioning valve by itself an unnecessary step? Or even a bad idea?

58Yeoman said:

My '58 Chevy has a single MC and drums all around. So did my '63 Galaxie. I always figured the OEM engineers knew what they were doing.

I don't want people to think I don't trust single reservoir master cylinders...I do. I put a new single master cylinder and had the original booster rebuilt in my '61 Mercury, and I'll drive it anywhere. I did that because it's a very original car and I wanted to maintain originality. If all the components of a single MC system are checked regularly, and are in good condition, I feel the systems are safe.

I put the dual reservoirs in my T-Bird and wagon because it was my understanding that there's even better safety with those types of systems. Thanks to this thread, I'm learning that the truth is more complicated than that, and will proceed from this point with that new understanding. I had never even heard of a PDV or a pressure residual valve before this thread. Many thanks to KULTULZ and others for the education on these type brake systems. I WILL follow up on this stuff for my car.

 

[KULTULZ]

BTW, what's the opinion (if any) on bleeding the proportioning valve during installation? I bench bled the master cylinder for my car and when it was installed I hooked up the lines to the proportioning valve and bled those components (with clear hoses back to the MC.) I don't think I read to do that in the manual or anywhere else, but it seemed like a good idea. Maybe it wasn't. Of course once I got all the other lines hooked up, I bled the whole system. Is bleeding the proportioning valve by itself an unnecessary step? Or even a bad idea?

Actually, unnecessary. The valve(s) would be bled during the complete system bleed procedure (after bench bleeding the MC).

The only time you should need to bleed a PDV is after a system failure and repair and the pintel fails to center after the system bleed. Then you would bleed line(s) @ the PDV until it centered.

I put the dual reservoirs in my T-Bird and wagon because it was my understanding that there's even better safety with those types of systems.

Thanks to this thread, I'm learning that the truth is more complicated than that, and will proceed from this point with that new understanding. I had never even heard of a PDV or a pressure residual valve before this thread.

And you are wise in your thinking. The only way I would use a single is if the car is a dedicated restoration. Even then, the fluid needs to be changed (flushed) at the least every two years.

In the photo you showed of the MC INSTALL -

I do not see a switch to activate a WARNING LAMP on the dash so it must just be an ADJ PPV?

Was the OEM PPV you removed a cylindrical cast iron or a brass valve?

Is there any way you can show or give the lengths of the two boosters? The aftermarket booster along with their MC gave you the clearance needed for the MC to clear the apron reinforcement?

 

[56sedandelivery]

My head hurts. I am sure I will be going through this when I get to that point.

 

[5851a]

Brakes are very complicated. The original engineers took into account weight or load of vehicle at the time of manufacture. They would vary brake shoe width, drum size, wheel and master cylinder size. They would alter suspension mounting points to reduce nose dive on panic stops. I can't out think an entire branch of Dearborn so I just stick with what Ford said was good for me at the time. I once owned a 64 Thunderbird with all drum brakes only modification was radial tires. It stopped good, not on a dime but enough to leave a goose egg on your forehead. I also still own a 78 5.0 Fairmont. I swapped in a rear end from a new 82 Mustang, the rear brakes would lock at slightest touch. All the brake parts were the same, except the wheel cylinders were 1/32? smaller on the Mustang rear. Installed new Fairmont cylinders and back to normal. That 1 tiny change made a world of difference. I understand dual circuit brakes but don't think they are going to save you. Maintenance and driver awareness will. Just my take on it. My wife of 30+ years knows couple of jobs I will not do for friends or family, 1 is brakes and other is automatic transmissions. FI cars is a close 3rd.

 

[KULTULZ]

All I know for sure, is every time one of my buddy’s bought a “kit” with a chrome valve I could never get it to not leak at the line fittings. Which was too bad, ‘cause they were sure the car was a 1/10th quicker in the 1/4 mile.

FWIW, one of those buddy’s put an ABS system on a 56 Nomad.

Disc for 14” rims on the front, dual master, combo valve, and booster. Works fine, once we traded the chrome combo valve for the plain brass one.

It might have gone quicker if there was no leakage ...

You know, that CHINESEUM FLASH CHROME cuts the wind resistance through the traps. All that flash under the hood helps confuse the TECH INSPECTOR and you can get away with more ...

The problem is that they allowed the plating to reach the threads. Hope they also use this on their tanks ...

 

[KULTULZ]

1955-1957 BIRD FRONT DISC CONVERSION​

New rear wheel cylinders are provided with the kit. The different diameter in them eliminates the need for a proportioning valve.

SOURCE - https://www.ctci.org/disc-brake-conversion/

The basic conversion kits for the Thunderbirds do not contain a combination valve.

Disc brakes without a proportioning/metering system will work.

SOURCE - https://www.ctci.org/disc-brake-performance/

In addition a 10 lb residual pressure valve can be installed in the fluid line to rear brakes. A residual pressure valve is a one way check valve that maintains enough pressure on the rear brakes to keep the shoes close to the drums without drag resulting in a firmer pedal.

SOURCE - https://www.ctci.org/disc-brake-performance/

Gil Baumgartner
CTCI Authenticity Chairman

... say what ... ?​

 

[KULTULZ]

- ADDENDUM CONTINUATION -

1955-1957 BIRD FRONT DISC CONVERSION​

In addition a 10 lb residual pressure valve can be installed in the fluid line to rear brakes. A residual pressure valve is a one way check valve that maintains enough pressure on the rear brakes to keep the shoes close to the drums without drag resulting in a firmer pedal.

SOURCE - https://www.ctci.org/disc-brake-performance/

A 10# RESIDUAL VALVE does not hold the shoes closer to the drum at rest. Only proper adjustment and/or self adjusters will do that.

The purpose of the valve is to not allow the wheel cylinder(s) pistons to slam shut after application release (return spring pressure) so as to prevent wheel cylinder cup shuddering allowing either fluid leakage and/or air ingestion.

And yes, it (RPV) does affect pedal height on a DISC/DRUM APPLICATION.

The industry went to WHEEL CYLINDERS with CUP EXPANDERS later to eliminate the valve but this was generally on a different style drum brake (not self-energizing).

Two types of COMBINATION VALVES shown below -

COMBINATION VALVE - A COMBINATION VALVE assembly consists of two or more individual brake valve(s) functions - PDV - PPV - METERING - RESIDUAL PRESSURE (Drum Brake Circuit)

TOP SHOWN - PDV and PPV

BOTTOM SHOWN - PDV - PPV - FRONT METERING

FORD usually had the RPV in the MC DRUM CIRCUIT FLUID OUTLET.

Gil Baumgartner
CTCI Authenticity Chairman

... say what ... ?​

... yes, I am retaining water but I hope this shows how important it is when buying a kit and/or making brake modification(s) a correct source of information is supplied.

And this is across the board.

 

[Gene F]

I changed over my 67 ElCamino to front disc, and DOT-4. I got the system from Performance Suspension Technologies. They were the vendor that for years advertised on the back cover of Hemmings. It worked perfectly. My advice, but an engineered system that way it will all work together.

 

[miker98038]

In line with what Gene said above, an acquaintance with a 56 Ford put a front disc system on from Prestige Thunderbird. He’s local and was able to go over and go thru it in detail. He was impressive with their knowledge and research, and has been pretty happy with it. There are some vendors who do have good systems and there are some who just throw parts in a box and ship it. The hard part is telling the difference.

I have an OT ‘67 with a well engineered and completely modified suspension, done by a major vendor. They told me the whole brake system was a Wilwood design, from the pedal ratio to the pads. All their parts and design. If I were ever to do a conversion again I’d look into it with them. Probably have a heart at when I got the price, but I’d bet it was right.

 

[KULTULZ]

Disc brakes became an option on some Ford vehicles from the factory in the early sixties. FoMoCo provided a proportioning system on all their vehicles as part of the overall package. The proportioning valve soon evolved into a combination valve which provided proportioned pressure to the rear brakes and metered pressure to the front disc brakes. The basic conversion kits for the Thunderbirds do not contain a combination valve.

Disc brakes without a proportioning/metering system will work.

CTGI -

Let's repeat that statement -

The basic conversion kits for the Thunderbirds do not contain a combination valve.

Disc brakes without a proportioning/metering system will work.

Sure they will ...

-'TYPICAL' BIRD FRONT DISC KIT-​

Upgrade your TBird with front disc brakes.

For added safety see combination valve sold seprately. Part# 2B257K

Actual shipping charges will be applied to this item.

This brake kit seems to be assembled by one company and sold through these BIRD VENDORS. DROP SHIP FREIGHT CHARGES indicates that.

On their 2018 catalog (PRESTIGE), there is no mention of a separate COMBINATION VALVE being available, although it seems someone at other vendors woke up at some point and offered them separately.

CTGI says their MC does not contain an RPV for the drum circuit and had to have an external installed. Most likely a CHI-COM MC.

This is what I am trying to get across. But I seem to be wasting my time.

 

[bobss396]

I keep it real simple. I still trust a single master system on drum brakes. Providing all components are in good shape. My Ford has a dual master and front discs. No fancy plumbing, just a distribution block that takes the old Ford pressure switch.

 

[KULTULZ]

I changed over my 67 ElCamino to front disc, and DOT-4. I got the system from Performance Suspension Technologies. They were the vendor that for years advertised on the back cover of Hemmings. It worked perfectly. My advice, but an engineered system that way it will all work together.

Just wondering, do you have the KIT PART NUMBER they sold you? Did it come with a GM STYLE COMBINATION VALVE or 'SPINNING FOR DOLLARS' bias valve? GM low drag calipers (METRIC) with quick take-up MC?

My Ford has a dual master and front discs. No fancy plumbing, just a distribution block that takes the old Ford pressure switch.

And this car is street driven?

 

[KULTULZ]

I keep it real simple. I still trust a single master system on drum brakes. Providing all components are in good shape. My Ford has a dual master and front discs. No fancy plumbing, just a distribution block that takes the old Ford pressure switch.

I did too until I learned the value of one when I went over an embankment in a 62 CHEV, convertible at that.

 

[KULTULZ]

Tagging these threads -

AXLE HOUSING SEALS -

https://www.fordbarn.com/forum/showthread.php?t=313498

BRAKE DRUM DIA - LINING WIDTH - LINING LENGTH

https://www.fordbarn.com/forum/showthread.php?t=314448

- within the discussion as it describes rear drum brake woes.

AND THIS - REAR BRAKE SELF-ADJUSTERS ADDITION -

https://www.fordbarn.com/forum/showthread.php?t=314775