Switching to a shared reservoir brake master cylinder

[Frankenchevy]

The pressure and pedal feel were great prior to tearing the truck down. Only thing that will be different when it’s back together are all new replacement components/lines, deletion of height sensing valve and new disc/disc prop valve.

I guess I’ll just run it as is and see what’s what.

 

[bucket]

You should be good then. As was mentioned, you can cut a slot in the divider wall, but I certainly wouldn't want to go too far with it. You still want some separation so if one of the circuits blows, you don't loose all braking pressure on both circuits. A small transfer slot will let the leaking circuit take just the "extra" fluid from the good circuit.

 

[smoothandlow84]

So restricting flow to the rear brakes will increase the pressure on the rear brakes?

That doesn't seem to add up.

Most of the power booster disc brake conversion kits on the market have a larger diameter...more volume hard line from the front circuit and a smaller line....higher pressure hard line dedicated to the rear. Even my 64 c10 had larger diameter front lines than rear. More volume wont necessarily equal high pressures, but a smaller diameter line will increase the pressure without the volume. The smaller diameter line restricts flow and increases the pressure output. With whatever he decides, a proportioning valve (adjustable) would be ideal so that he can accomolish the ratio and pedal feel that makes him comfortable and safe. I wouldn't suggest drilling or re-engineering the resevoir. The auto engineeres r &d department have spent years figuring it out already. I would leave sleeping dogs lie.

 

[Blue Ox]

Most of the power booster disc brake conversion kits on the market have a larger diameter...more volume hard line from the front circuit and a smaller line....higher pressure hard line dedicated to the rear. Even my 64 c10 had larger diameter front lines than rear. More volume wont necessarily equal high pressures, but a smaller diameter line will increase the pressure without the volume. The smaller diameter line restricts flow and increases the pressure output. With whatever he decides, a proportioning valve (adjustable) would be ideal so that he can accomolish the ratio and pedal feel that makes him comfortable and safe. I wouldn't suggest drilling or re-engineering the resevoir. The auto engineeres r &d department have spent years figuring it out already. I would leave sleeping dogs lie.

Your hydraulic theory seems to be based on aerodynamics. Smaller diameter lines do not increase pressure at the wheels, except maybe when you're trying to get the brakes to release. Restricting brakes lines creates undesireable effects all the way around.

I do agree to let the engineers do their jobs and if his system worked fine before he probably should leave it alone and see how it works when he has it all back together.

 

[smoothandlow84]

Your hydraulic theory seems to be based on aerodynamics. Smaller diameter lines do not increase pressure at the wheels, except maybe when you're trying to get the brakes to release. Restricting brakes lines creates undesireable effects all the way around.

I do agree to let the engineers do their jobs and if his system worked fine before he probably should leave it alone and see how it works when he has it all back together.

Correction....fluid dynamics.



So you are saying that a smaller diameter line with the same amount of fluid passing will not resteict flow causing a higher fluid line pressure?.....interesting. Last time I checked in the case of the fire department, they are able to increase the velocity and or pressure of the water in the hose by restricting the flow with a smaller diameter nozzle size...smaller size opening, same volume, higher pressure. If you dont believe me, try it out on your garden hose. Smaller diameter nozzles and line diameters are also used in water jetting applications as well...just saying.

Pressure changes can be manipulated when used in conjunction with restricted flow rates.

 

[bucket]

Correction....fluid dynamics.



So you are saying that a smaller diameter line with the same amount of fluid passing will not resteict flow causing a higher fluid line pressure?.....interesting. Last time I checked in the case of the fire department, they are able to increase the velocity and or pressure of the water in the hose by restricting the flow with a smaller diameter nozzle size...smaller size opening, same volume, higher pressure. If you dont believe me, try it out on your garden hose. Smaller diameter nozzles and line diameters are also used in water jetting applications as well...just saying.

Pressure changes can be manipulated when used in conjunction with restricted flow rates.

But there's way more variables than that. Wheel cylinders or calipers are nothing like a nozzle. Unless they are blown out, but then you've got other problems.

Speed or velocity has very little to do with brake system components. It's a fully closed, dead end system. And there's no pump that is capable of building a certain amount of pressure, just a human foot.

 

[73c20jim]

Me, I'll mess with a lot of ****, BUT NEVER BRAKES.

 

[Blue Ox]

Correction....fluid dynamics.



So you are saying that a smaller diameter line with the same amount of fluid passing will not resteict flow causing a higher fluid line pressure?.....interesting. Last time I checked in the case of the fire department, they are able to increase the velocity and or pressure of the water in the hose by restricting the flow with a smaller diameter nozzle size...smaller size opening, same volume, higher pressure. If you dont believe me, try it out on your garden hose. Smaller diameter nozzles and line diameters are also used in water jetting applications as well...just saying.

Pressure changes can be manipulated when used in conjunction with restricted flow rates.

Sure, a restriction will cause higher pressures at the pressure source / master cylinder.. How does that help the situation at the wheel?

 

[smoothandlow84]

It should react as a complete circuit . Less pressure at the brake pedal, transferred through the circuit (brake line) to the caliper. Power assisted brakes along with line restrictions will ultimately lead to more pressure (stiffer pedal, more pressure with less pressure applied at the brake pedal). Compare how much muscle power used to be required before the advent of power assisted hydraulic brakes.

I dont claim to be an expert, only going off of my own trial and error over the years. It all comes down to personal preference and what you want to feel with the pedal. There has been alot of discussion regaring what size brake lines work best. Im my experience, bigger isnt always better. The bigger the brake lines used tends to decrease the amount of pressure from the caliper. With that in mind, your brake system still requires volume as well to work properly.

 

[smoothandlow84]

But there's way more variables than that. Wheel cylinders or calipers are nothing like a nozzle. Unless they are blown out, but then you've got other problems.

Speed or velocity has very little to do with brake system components. It's a fully closed, dead end system. And there's no pump that is capable of building a certain amount of pressure, just a human foot.

Maybe I am not fully understanding your statement here.........

Actually, speed, weight and velocity all effect brake system components. The more speed and mass of an object, the longer distance it will take to stop the object. What about brake fade....brakes get overworked and fail due to extreme and prolonged heat often caused by excessive weight and or speed. Bigger brake contact area (larger diameter brakes) as well as faster heat dissapating components all increase the ability to stop a vehicle (i.e. carbon fiber rotors and pads used in F1). The human foot along with a "pump" whether it be a hydro boost circuit or vacuum boost will both multiply the effect of ones foot when the pedal has been depressed. This was the main reason why manual brakes along with a single fluid resevoir were replaced with a dual unit and power assisted brake system components.

 

[bucket]

Maybe I am not fully understanding your statement here.........

Actually, speed, weight and velocity all effect brake system components. The more speed and mass of an object, the longer distance it will take to stop the object. What about brake fade....brakes get overworked and fail due to extreme and prolonged heat often caused by excessive weight and or speed. Bigger brake contact area (larger diameter brakes) as well as faster heat dissapating components all increase the ability to stop a vehicle (i.e. carbon fiber rotors and pads used in F1). The human foot along with a "pump" whether it be a hydro boost circuit or vacuum boost will both multiply the effect of ones foot when the pedal has been depressed. This was the main reason why manual brakes along with a single fluid resevoir were replaced with a dual unit and power assisted brake system components.

Speed/velocity as far as brake fluid movement. Nothing about the vehicle travel itself.

 

[smoothandlow84]

Speed/velocity as far as brake fluid movement. Nothing about the vehicle travel itself.

Got it. I didn't think we needed to discuss the physics involved...lol

 

[bucket]

As far as brake line sizing, most manufacturers have all seemed to agree on 3/16 line for supplying fluid to a single wheel. A line supplying 2 wheels, like rear brakes on a solid axle, is usually 1/4 inch. It can better support the fluid requirements for two rear brake components, as the line itself being a restriction is not desirable.

 

[smoothandlow84]

The pressure and pedal feel were great prior to tearing the truck down. Only thing that will be different when it’s back together are all new replacement components/lines, deletion of height sensing valve and new disc/disc prop valve.

I guess I’ll just run it as is and see what’s what.

I think you are off to a good start. A high quality adjustable proportioning valve is the key. I personally prefer my brakes to be 70 percent front, 30 percent rear when disc/disc for daily drivers. On a road couse, depending on how many turns and the average degree of each turn......and the weight of the vehicle, it can vary from 75 percent to as much as 85 percent going to the front. On circle track I would dial in the brakes almost even. Even though its been a few years since being on a track, I still like to play around now and then. More often than not, I spend more time off road racing. Brakes are still very crucial regardless. Offroad is more a balance of power, suspension AND brakes.

 

[smoothandlow84]

As far as brake line sizing, most manufacturers have all seemed to agree on 3/16 line for supplying fluid to a single wheel. A line supplying 2 wheels, like rear brakes on a solid axle, is usually 1/4 inch. It can better support the fluid requirements for two rear brake components, as the line itself being a restriction is not desirable.

I agree. With my disc brake conversion on my 64 c10, I also opted to run seperate circuits from the proportioning valve body to each front brake and the usual single line for the rear brakes. The proportioning valve on most vehicles only offers one circuit for front and rear, but my setup was an upgrade with more built in fail safe. I didnt have to run seperate front circuits, but the valve gave me the option to do so.

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