BRAKE THEORY 001 - H.A.M.Bone

[KULTULZ]

They are still at it over there -

https://www.jalopyjournal.com/forum/threads/help-with-brake-combination-valve-question.1307162/

I have it on jackstands in the front and tires on the ground in the rear. When I tested my booster install without the engine running and I press hard on the pedal and use a metal pipe to keep the brake pedal pushed in, I can still spin the front tires a bit but feel a little more resistance than with the pedal not pressed in. Does anyone know if I have an issue that requires adjusting the proportioning in this setup? I'm not even sure if it can be adjusted? I also thought maybe its doing this because more of the weight is on the rear with it on jackstands in the front. It seems to lock the front wheels ok when the engine is running but I wanted to verify my setup is sound with just manual brakes as well.

 

[Gene F]

Kultulz, I am not a member over there. However, I can see his photos. My streetrod has underfloor brakes. I found out with residule valves you can not effectively bleed brakes with a vac gun. And the first step should NOT be to have the assistant start off by pumping the brakes up before cracking the bleeder valves. All that does is broadcast air bubble throughout the system. My Dad is the worst, so I bleed brakes with my wife. LOL

 

[miker98038]

The brake problems and information on all the auto sites is all over the place. Good, bad, dangerous, you name it. I just went thru that on a friends car. The right front caliper partially locked up and being pissed off, he drove it home. That was problem 1. Right front bearing disintegrated from heat. Rotor blue. All the high temp wheel bearing grease in a puddle in the hub cover. I call that pilot error.

But with everything replaced, the front wouldn’t bleed. That “combination” valve had failed in the closed position (which some say they do and some say they don’t) but all it would do is dribble fluid. The supplier still had his 10+ year old order and sold him a replacement. Different unit (we don’t use that one anymore) and we finally got it on the road. After finding an odd ball adapter to hook the rear lines up due to a fitting mis match.

My cars have residual valves as required and adjustable pressure valves to the rear. Linings that match. Pressure checks at the wheel. They work well but it’s complicated, fairly expensive, and requires someone who really knows what they’re doing. No “combination” valves from some other system because it’s available cheap.

What amazes me is we don’t see more braking related accidents on hot rods. Must be because we’re all older and driving careful.

 

[KULTULZ]

Here It Is In A Nutshell -

- 1300HP MERC COMET BRAKE FAILURE -​

https://www.reddit.com/r/cars/comments/vups2d/1300hp_mercury_comet_crashes_due_to_brake_failure/

 

[KULTULZ]

See if this ill shows large enough to cipher -

Unbelievably sloppy install.

 

[Ford blue blood]

Brake line mounted under the frame?

 

[56sedandelivery]

Question. With 4 wheel disc brakes do you have this problem?

 

[KULTULZ]

Brake line mounted under the frame?

You are the astute one ...

 

[KULTULZ]

Question. With 4 wheel disc brakes do you have this problem?

Yes, unless allowed for.

The main thing is that the early cars had the MC mounted on the frame rail under the driver's floorboard (before swing pedals). That would put the MC reservoir below the wheel cylinder/caliper and gravity would cause the brake fluid to drain back (gravity) to the MC, resulting in a soft pedal on first application.. A 2# RESIDUAL VALVE needs to be plumbed in to hopefully prevent that on DISC APPL.

The 10# RESIDUAL VALVES needed with drum brakes (at that period) would cover DRUM but DISC would always have a slight drag on the rotors with the 2# RV. If you mounted four wheel disc, the problem would be worse.

 

[Gene F]

photo look clear to me

 

[Ford blue blood]

A Good friend whom I was assisting with his build mounted the master on the frame rail. Disc/disc setup. His reservoirs were on the fire wall. Convincing him that residuals were not required because the reservoirs were above the wheel cylinders ended up with "pull the brake lines off the master and watch the fluid run all over the place". After the mess was cleaned up he conceded. Mean ol Mr. Gravity keeps thing tight when the reservoir is above the wheels!

 

[KULTULZ]

A Good friend whom I was assisting with his build mounted the master on the frame rail. Disc/disc setup. His reservoirs were on the fire wall. Convincing him that residuals were not required because the reservoirs were above the wheel cylinders ended up with "pull the brake lines off the master and watch the fluid run all over the place". After the mess was cleaned up he conceded. Mean ol Mr. Gravity keeps thing tight when the reservoir is above the wheels!

... hmmpf ...

I have no experience with this type of braking, so bare with me please.

So the theory is to use a frame rail mounted MC without reservoir(s) and the weight of the fluid in the remote reservoir(s) and lines will prevent the brake fluid from draining back (gravity) from the caliper (without a RV) as the MC itself will be/remain full?

Eliminating the RV would rid the problem of a slight drag on the rotor.

 

[KULTULZ]

Just like the ENERGIZER BUNNY, it keeps going and going ...

To Wit -

https://www.jalopyjournal.com/forum/threads/pedal-travel-brakes.1307775/

Bought a cpp 1" master cylinder with build in proportioning valve.

I think he is making a tanker and runnin' shine with those copper worms ...

 

[KULTULZ]

... ...

- I'LL BE DAMNED ... IT'S TRUE! -​

CPP Master Cylinder, MCPV-1, Polished Aluminum, 1" Bore -

Weighing in at only five pounds, the MCPV-1 aluminum master cylinder has all the features of a modern braking system in one master cylinder. It has a double-adjustable proportioning valve, removable metering valve (for 4-wheel disc brake cars), stop light switch port, larger capacity (1-quart) and a smaller size than a conventional iron master cylinder. It's approximately the same size as an iron Corvette master cylinder, only much lighter. The MCPV-1 has two circuits: a front circuit with a metering valve for disc front/drum rear brakes, which is removable for 4-wheel disc brakes and a rear circuit that has the double-adjustable proportioning valve and a maximum rear pressure adjustment. The proportioning valve controls the brake pressure between front and rear brakes, while the rear pressure adjustment controls what the maximum pressure is to the rear brakes.

Available with a polished finish.

SOURCE - https://www.opgi.com/brake-systems/...-mcpv-1-polished-aluminum-1-bore-ch26656.html

 

[Ford blue blood]

... hmmpf ...

I have no experience with this type of braking, so bare with me please.

So the theory is to use a frame rail mounted MC without reservoir(s) and the weight of the fluid in the remote reservoir(s) and lines will prevent the brake fluid from draining back (gravity) from the caliper (without a RV) as the MC itself will be/remain full?

Eliminating the RV would rid the problem of a slight drag on the rotor.

That is correct. If you look down the reservoir you can see the piston opening to the bore. Push the piston in and it closes the reservoir from the piston and compresses the fluid to operate the brakes. Release the piston and you can see some of the fluid return to the reservoir , especially if looking at the drum side.

 

[KULTULZ]

I was describing a MC without the reservoir integral or the reservoir atop the MC (closed except for fill and outlet fittings).

If remote as you describe (firewall mounted), the weight of the fluid (in the reservoir(s) and lines) would preclude the front caliper line draining back after pressure release to the MC due to gravity?

He had no soft pedal/slow take-up after that (removal of the external #2 RPV)? Does he have the GM METRIC CALIPERS?

Like I said, I never fooled with anything this early so I am on a learning curve.

 

[Ford blue blood]

Yes, that is correct. He used a "regular" Corvette master with a modified top, aluminum with fittings for the lines to the remotes. Look inside a regular master and watch the cylinder when pushing the pedal. Again a 4 disc setup.

He had perfect pedal feel and response. Firebird rear disc, after market kit for the front, 11" rotors. I drove the car for a young lady's wedding and put about 150 miles on it. Never felt funny or out of sorts. He has unfortunately passed and I sold the car for the widow to a fellow in WA. The pictures I had are unfortunately on the failed hard drive from my now dead old machine....

 

[KULTULZ]

Question. With 4 wheel disc brakes do you have this problem?

If you have an OEM vehicle that came through with four wheel disc, no.

EDIT - 17FEB2024

[Let me qualify the above statement. There are DISC/DISC PPV's. Usually, when OEM designs a four wheel disc car, the front and rear systems are balanced by design (same as a four wheel drum car) or operated with ABS. If the builder uses differing rated vehicle braking ends, there may/will be a need for a PPV. Same situation on a rear disc swap. The vehicle ends will not be matched (same as a DISC/DRUM swap).]

If one retrofits a car with front and rear disc that the wheel ends are from differing vehicle(s), chances are yes. Even some OEM installs will use a DISC/DISC COMBINATION VALVE (PDV and PPV - NO METERING and/or RESIDUAL PRESSURE VALVE) to allow for any inherent imbalance.

Say you have a car and use GRANADA DISC front and later style CROWN VIC disc on the rear. There is no way that they can work together correctly. One will overpower the other at some point, especially on a panic brake application. Then you go to PPV(s).

And we haven't gotten to the correct style MC for DISC/DISC and the amount of fluid volume needed to move the chosen caliper pistons correctly. A lot to cipher on and most of these so-called kit makers haven't the faintest clue or concern.

WILWOOD offers correct balanced DISC/DISC (as I am sure of others) kits but I have never checked the offered kits and what they fit.

 

[KULTULZ]

- ANOTHER CONTINUING SAGA ENTRY IN THE USUAL FASHION -​

TO WIT - https://www.jalopyjournal.com/forum/threads/wheel-cylinder-travel.1309066/

 

[KULTULZ]

The brake problems and information on all the auto sites is all over the place. Good, bad, dangerous, you name it. I just went thru that on a friends car. The right front caliper partially locked up and being pissed off, he drove it home. That was problem 1. Right front bearing disintegrated from heat. Rotor blue. All the high temp wheel bearing grease in a puddle in the hub cover. I call that pilot error.

But with everything replaced, the front wouldn’t bleed. That “combination” valve had failed in the closed position (which some say they do and some say they don’t) but all it would do is dribble fluid.

The PRESSURE DISTRIBUTION VALVE failed or the system was not bled correctly.

When bleeding a DUAL RESERVOIR MC SYSTEM (w/ PDV included), you always use a shutter valve centering tool in the PDV (replaces switch) for the bleeding process. If that shuttle pins moves to one side or another during bleeding, it is going to interfere with fluid pressure/volume in either of the circuits -