Front Disc brake MC

[triracer67]

Using Jeff’s disc brake kit which I believe has GM calipers. MC that came with kit is power with fittings on passenger side. I’m look to keep manual so need new MC with fittings on driver side. What year stock MC can I use? I do have a proportioning valve from previous build if one is needed?

 

[DirtDonk]

What piston size are you looking for? To get the driver's side ports, you can source any '71 or later Bronco master, as long as it's for manual brakes.
These will work fine with the smaller Ford calipers, but might be too small for the GM calipers. Other members here will have some feedback regarding piston size vs caliper size.
The Ford based ones are either 7/8" or 1" diameter (I can't remember). You really want a 1, to 1 1/8" master, but by the time you get to over 1" diameter, you also benefit greatly by going with a booster.
For manual, you can check out a mid-sixties Corvette with manual brakes. Usually about 1" if I remember, but I don't remember what side of the body the ports are on.
This is one of the reasons we sell masters with ports on both sides! You can see our #3083 which is an aluminum version of what a Corvette master looks like. But it has ports on both sides (unless we've changed sources) as it's a "universal" type brand new master.
Our #3140 is a stock replacement. Which, again, is potentially too small for your calipers with larger pistons. Giving more pedal travel than some might like.

Paul

 

[triracer67]

What piston size are you looking for? To get the driver's side ports, you can source any '71 or later Bronco master, as long as it's for manual brakes.
These will work fine with the smaller Ford calipers, but might be too small for the GM calipers. Other members here will have some feedback regarding piston size vs caliper size.
The Ford based ones are either 7/8" or 1" diameter (I can't remember). You really want a 1, to 1 1/8" master, but by the time you get to over 1" diameter, you also benefit greatly by going with a booster.
For manual, you can check out a mid-sixties Corvette with manual brakes. Usually about 1" if I remember, but I don't remember what side of the body the ports are on.
This is one of the reasons we sell masters with ports on both sides! You can see our #3083 which is an aluminum version of what a Corvette master looks like. But it has ports on both sides (unless we've changed sources) as it's a "universal" type brand new master.
Our #3140 is a stock replacement. Which, again, is potentially too small for your calipers with larger pistons. Giving more pedal travel than some might like.

Paul

Follow up question, if I go to the larger bore corvette, do I need to shorten the piston?

 

[DirtDonk]

You never shorten a piston. The master cylinder is assembled. The piston is not adjustable.
It is what it is.
The only thing you need lengthen or shorten is the rod between the pedal and the back of the master.
Same goes for adjusting rods in the cantilever bracket for power boosters.

You also need to make sure that you have a deep well piston for manual brakes. Meaning that the pocket where the rod goes is deep so that it doesn’t pop out.
Manual Brakes typically had a deep well and a clipped in rod. Whereas power assist brake master cylinders had a shallow well so that the short Booster rod could reach the pistol.
That’s why many masters these days come with the deep well, and a “bullet “ shaped spacer to fit between the rod and the piston.
You might be able to shorten the spacer without trouble, but that would be the only piece you could modify on the master.

 

[DirtDonk]

For different size pistons, you’re not changing the length of the stroke. If that’s what you meant. You’re changing the diameter of the piston to increase or decrease the amount of fluid flow. And the amount of “leverage“ if that’s the proper term. Meaning the master to slave ratio.

 

[ntsqd]

Despite being told repeatedly what it is, I don't have the EB brake pedal ratio in my memory. It is in my notes at home. Should someone recall what it is, feel free to post it.

First though, we need to know your preferences for pedal feel. Do you prefer a hard pedal or a soft pedal? Brakes are highly subjective and it's hard to say what will work the best for you without knowing this.

 

[toddz69]

Despite being told repeatedly what it is, I don't have the EB brake pedal ratio in my memory. It is in my notes at home. Should someone recall what it is, feel free to post it.

6:1.

Todd Z.

 

[toddz69]

Using Jeff’s disc brake kit which I believe has GM calipers. MC that came with kit is power with fittings on passenger side. I’m look to keep manual so need new MC with fittings on driver side. What year stock MC can I use? I do have a proportioning valve from previous build if one is needed?

If you're keeping the rear drums with it, I'd start by trying a stock EB drum master cylinder with the residual pressure valve removed. 1" bore.

Todd Z.

 

[ntsqd]

Looks like GM D52 calipers to me.
20+ years ago my brake design mentor taught me to look at the overall leverage ratio for the front brakes to estimate pedal feel. I'm sure that he's progressed far beyond this by now. I've just been out of that loop for a long time.
Here's the math:

Caliper	Caliper Piston #1 Ø	Caliper Piston #1 Area	M/C Piston Ø	M/C Piston Area	Pedal Ratio	Hyd Ratio	O/A Ratio
Ford 2-7/8"	2.9375​	6.7771​	0.9375​	0.6903​	6.00​	19.64​	117.81​
Ford 2-7/8"	2.9375​	6.7771​	1.0000​	0.7854​	6.00​	17.26​	103.55​
Ford 2-7/8"	2.9375​	6.7771​	1.0625​	0.8866​	6.00​	15.29​	91.72​
Ford 2-7/8"	2.9375​	6.7771​	1.1250​	0.9940​	6.00​	13.64​	81.81​
Ford 2-7/8"	2.9375​	6.7771​	1.2500​	1.2272​	6.00​	11.05​	66.27​
Ford 2-7/8"	2.9375​	6.7771​	1.3125​	1.3530​	6.00​	10.02​	60.11​

GM D52 2-15/16"	2.9375​	6.7771​	0.9375​	0.6903​	6.00​	19.64​	117.81​
GM D52 2-15/16"	2.9375​	6.7771​	1.0000​	0.7854​	6.00​	17.26​	103.55​
GM D52 2-15/16"	2.9375​	6.7771​	1.0625​	0.8866​	6.00​	15.29​	91.72​
GM D52 2-15/16"	2.9375​	6.7771​	1.1250​	0.9940​	6.00​	13.64​	81.81​
GM D52 2-15/16"	2.9375​	6.7771​	1.2500​	1.2272​	6.00​	11.05​	66.27​
GM D52 2-15/16"	2.9375​	6.7771​	1.3125​	1.3530​	6.00​	10.02​	60.11​

Ideal O/A Range is 93:1 to 95:1, Less = Stiff pedal that is hard to stop, more than 95:1 can range out to about 100:1 before everyone will complain about mushy brakes. Some will complain at 96:1

 

[acropilot]

I'm running the same front caliper disc brake set up as you and am running a 7/8" bore wilwood mc since redoing my Bronco a second time over.It stops as good as the stock booster mc setup that i had when i first built my Bronco 17 yrs ago but has a much cleaner look and also has a good pedal feel also.I tried a 15/16"bore corvette style mc and it worked ok but the 7/8" bore works better. I'm running 33-12.50-15 tires.

 

[ntsqd]

From what I've seen over the years the 100:1 boundary is far less definite than the 93:1 boundary. Assuming a stock pedal acropilot's EB is at 117:1 O/A leverage. That's about as far in that direction that I can ever recall seeing with the driver liking it. Most would find the pedal feel too mushy, but as I said earlier pedal feel is highly subjective and there is no wrong answer.

 

[acropilot]

For what ever reason my setup works great. Pedal feel is nice and firm with the pedal travel being what i would consider normal.I am running the lines through a disc /drum combination valve.