Booster/Master Cylinder Upgrade?

[1984RESTOMOD]

Running discs front(D35) and rear(8.8") on my '84. Curious if I should upgrade my booster/master cylinder from what was factory that year given my front is from a '92 ranger and rear from a '96 explorer. If so what options do I have besides hydroboost?

 

[maddyn]

off hand, you can upgrade to the master cylinder from the explorer and the bore size is a little bigger than the Ranger which should give you a little more pressure

 

[Shran]

If you're happy with the brake performance now, leave it alone. The master cylinder by itself won't add much... sometimes it can help with other issues though. I swapped in a later model master cylinder from an Explorer way after I did my disc swap - the factory one was not allowing much fluid to the rear brakes, I could tell they were just barely working by the rust forming on the rotors. New master cylinder fixed that BUT it could have just been a problem with the original part and not really that the "upgrade" fixed it.

off hand, you can upgrade to the master cylinder from the explorer and the bore size is a little bigger than the Ranger which should give you a little more pressure

That is not necessarily true, the bore size on both ends is what matters. Sometimes a smaller bore pushing fluid into a bigger bore is better than the other way around or vise versa. I don't know exactly how to calculate it but from experience playing with clutch master & slave bore sizes, I found that changing one without changing the other can have some unintended consequences - IE, increased pedal effort.

 

[JoshT]

Moving to an Explorer master would probably be beneficial for the rear brakes. Not sure how it will play with the front, the Ranger and Ex may have the same calipers and it not change much there.

IIRC there is some internal proportioning difference between a disc/drum master and a disc/disc master. The disc/drum masters also have a restrictor or valve in them to keep slight pressure on the rear wheel cylinders. I think it's to keep the shoes from moving far from the drum. Been a long time since I looked into it.

 

[SenorNoob]

Always heard it was a bad idea, but I've got 96/97 dual pistons up front and 01 Explorer rear out back and haven't had a single problem with my stock master cylinder except for the reservoir rotting off. So I replaced it with the same part. Stops faster than my wife wants it too. It scares her.

 

[mikkelstuff]

Hydroboost is absolutely worth the effort if you are up to it. As I understand it, the hydroboost from a Ford Astrostar van is fairly adaptable.

I have not tried this conversion on my '02 Ranger but did do a hydroboost conversion on my '75 Ranchero last summer. I'm still stunned by the braking power!

 

[Shran]

I don't really understand why dual piston calipers are better but I guess I am not a brake engineer. More parts to fail in my mind and having driven Rangers with dual piston front calipers vs my old '93 with singles, I can't tell a difference. I hate slide bolt style calipers & brackets too - way more maintenance and failure points than the old hammer in rectangle pins.

Chevy Astro van hydroboost units are also pretty popular to swap in, getting hard to find though, those vans are getting to be few and far between too bad, those were really good vehicles.

 

[Josh B]

Just how fast are you driving that thing?
How is that rear working on your Ranger? I'm thinking someday use the one off my 96 Explorer on the 93 Ranger, is it worth the effort?

 

[sgtsandman]

I don't really understand why dual piston calipers are better but I guess I am not a brake engineer. More parts to fail in my mind and having driven Rangers with dual piston front calipers vs my old '93 with singles, I can't tell a difference. I hate slide bolt style calipers & brackets too - way more maintenance and failure points than the old hammer in rectangle pins.

Chevy Astro van hydroboost units are also pretty popular to swap in, getting hard to find though, those vans are getting to be few and far between too bad, those were really good vehicles.

I think the benefit of the dual piston is that caliper clamping force is spread over a wider area, thus more even. I don't think they provide more clamping power since the rest of the system is still the same.

Not ever having one next to the other to compare, I can't say if the dual piston has a bigger pad area than a single. If it does, then it would theoretically brake better.

I think the dual piston rotors are bigger. So the moment arm for braking force would be bigger.

Since I don't have stuff to compare side by side, this is all theoretical.

 

[don4331]

The high school physics:

Single piston calipers have a piston diameter of 66mm = 5.30 in^2 for fluid to press against.
Rotors for aforementioned calipers are 10.87in diameter or 5.44 in radius
Braking force = distance * area * pressure (5.44 in * 5.30in^2 * 1 lb/in^2)
So, for every lb pressure of brake fluid acting on caliper piston, you get 28.8 in. lbs. of braking force on the rotor

Dual piston calipers have a piston diameter of 46mm = 2.58 in^2 for fluid to press against, but there are 2, so total area 5.15in^2 (note slightly less than the single pistons).
But because the single pistons are 20mm smaller in diameter (10mm/0.39in radius), engineers could make slightly larger rotors without caliper coming in contact with the rim - 11.26in diameter or 5.63 in radius
Braking force = distance * area * pressure (5.63 in * 5.15in^2 * 1 lb/in^2)
So, for every lb pressure of brake fluid acting on caliper piston, you get 29.0 in. lbs. of braking force on the rotor

For all intents, identical. (Ford could have actually went all the way to 11.66in diameter rotors with dual pistons had they felt the need)

Note: Pad area is irrelevant - At least for high level discussion.

There are some subtle advantages of spreading force over length of pad versus centralized, but that gets into complex calculations, beyond this forum.

 

[alwaysFlOoReD]

The high school physics:

Single piston calipers have a piston diameter of 66mm = 5.30 in^2 for fluid to press against.
Rotors for aforementioned calipers are 10.87in diameter or 5.44 in radius
Braking force = distance * area * pressure (5.44 in * 5.30in^2 * 1 lb/in^2)
So, for every lb pressure of brake fluid acting on caliper piston, you get 28.8 in. lbs. of braking force on the rotor

Dual piston calipers have a piston diameter of 46mm = 2.58 in^2 for fluid to press against, but ther are 2, so total area 5.15in^2 (note slightly less than the single pistons.
But because the single pistons are 20mm smaller in diameter (10mm/0.39in radius), engineers could make slightly larger rotors without caliper coming in contact with the rim - 11.26in diameter or 5.63 in radius
Braking force = distance * area * pressure (5.63 in * 5.15in^2 * 1 lb/in^2)
So, for every lb pressure of brake fluid acting on caliper piston, you get 29.0 in. lbs. of braking force on the rotor

For all intents, identical. (Ford could have actually went all the way to 11.66in diameter rotors with dual pistons had they felt the need)

Note: Pad area is irrelevant - At least for high level discussion.

There are some subtle advantages of spreading force over length of pad versus centralized, but that gets into complex calculations, beyond this forum.

But you're not using the full radius of the rotor, only the ~1.5"x3.5" of the pad at "x" distance from center of rotor. Now the "x" distance from center probably makes a difference? It must, just like a longer lever can move the world...

 

[don4331]

But you're not using the full radius of the rotor, only the ~1.5"x3.5" of the pad at "x" distance from center of rotor. Now the "x" distance from center probably makes a difference? It must, just like a longer lever can move the world...

That's what I get for a little simplification:

True, the calipers are designed so the piston center is aligned with the pad centerline. But that is equal between both calipers as pads are basically same size: Using ~1.5"x3.5" for the pads - so remove ~3/4" from both.

Single piston: 5.30 * (5.44-0.75) = 24.8​

Dual piston: 5.15 * (5.63-.75) = 25.1​

Still basically the same, just a little less force from both.

 

[SenorNoob]

So mathematically the best braking system is the one that works correctly. Nothing more.