Disc/Disc Master Cylinder for Bronco II

speedysprocket · May 4, 2018

So I put Mustang discs on the rear of my 85 Bronco II without changing the master cylinder and they're definitely not working as hard as the fronts. With a lot of hard braking around the block, front rotors will be about 220 degrees while rears around 110.
I know there's no proportioning valve to change.
I also know discs and drums work on different principles- drums cylinders use a small volume of high pressure while disc calipers move a lot of volume at a lower pressure.
So what disc/disc master cylinder bolts up? I looked at the Mustang and Explorer ones, but they seem to have metric flare nut threads while the stock is SAE. Is the only and best option to run the Mustang and change the brake lines, or is another master cylinder hiding out there somewhere?
Thanks!

dirtcowboy · May 4, 2018

I used an F-350 master, made my own lines. Brakes all day, every day and twice on Sundays!

BlackBII · May 4, 2018

dirtcowboy said:
I used an F-350 master, made my own lines. Brakes all day, every day and twice on Sundays!

Do you have a part number and pics?

speedysprocket · May 5, 2018

dirtcowboy said:
I used an F-350 master, made my own lines. Brakes all day, every day and twice on Sundays!

What year F350?

adsm08 · May 5, 2018

I used a 95 non-ABS Explorer master and just got the proper line adapter.

lvwill · May 5, 2018

I used a 96 explorer master and it bolted right up. Had to adjust the pushrod a little shorter but that's it.
On a 92 ranger.

dirtcowboy · May 5, 2018

I will get pics and part #,s tomorrow.

dirtcowboy · May 6, 2018

This is the brake master cylinder for an '86 Ford F-350 that I used on my BII. I compared it to an AC Delco unit my local NAPA had on the shelf, they were the same. The MC has 1 1/8" piston bore, moving lot's more fluid. Cammeddrz posted this setup before, and I copied his idea. http://www.therangerstation.com/forums/showthread.php?t=89225 Read this post as it also describes switching the brake lines on the MC. I also had a Wilwood prop valve but I haven't needed to use it.

BYPASS THE RABS CRAP!!!!! BYPASS THE RABS CRAP!!!!!

I also had to grind the MC a bit to make the bolt holes wider, I used a simple carbide bit and my electric drill, it took about 2 minutes to do.

https://www.amazon.com/Dorman-M39445-Brake-Master-Cylinder/dp/B001PYNY6C/?tag=959media-20

Installed pic

The lines pictured were made with the cheap crap, they are a cool green now.

I originally bought bulk brake line from Amazon, but I couldn't get it to flare properly. After further inspection I found that the tubing was produced with the fluid transport port about 1.5 RCH to one side, making it impossible to get a proper flare, so I trashed it. NAPA has some 3/16 brake line that has a cool dark green finish. I needed 10' 2" of line. I bought a 72" and a 51" piece, with a brass union and it worked out great, at a cost of about $16.00.

Like I said, brakes for days!

Oh, yeah, HE'S OUT OF THE GARAGE!!!!!

speedysprocket · May 6, 2018

I saw there are some new OEM Ford Explorer ones on eBay that appear to even include the proportioning valve at pretty reasonable prices. I might just grab one of those and then figure out the lines.

speedysprocket · May 11, 2018

I bought a 97 explorer master cylinder on eBay with the proportioning valve. Looks like the front is a DIN flare and the rear valve is an SAE double flare? Can anyone confirm and the thread sizes?

speedysprocket · May 23, 2018

Well put the 1995-97 master cylinder in. Pedal is nice and hard, but I still have to stand on it to get the truck to stop, and I still can’t lock a tire up. I hear them working hard like they’re about to skid, but they don’t. Is there a stronger booster that could be helping me? Or is this just Bronco II fate for stock front brakes with 33” tires?

speedysprocket · May 31, 2018

For anyone interested, I pulled the booster out of a 1998 explorer sport. It’s both a larger diameter and longer than stock Bronco II.
To fit, I had to elongate the firewall/pedal box holes, cut the push rod and weld the stock one on because the explorer was too short, and grind down the steering joint tabs that were hitting the larger booster.
The result was maybe slightly better braking, but with noticeably less effort.
I think the only thing that would improve more are better pads, maybe like EBC.

Potone1 · Aug 9, 2019

BlackBII said:
Do you have a part number and pics?

dirtcowboy said:
I used an F-350 master, made my own lines. Brakes all day, every day and twice on Sundays!

What benefit do you get from a larger bore master cylinder?

85_Ranger4x4 · Aug 11, 2019

Potone1 said:
What benefit do you get from a larger bore master cylinder?

Moves more fluid for altered braking setups.

I put an Explorer 8.8 in with disk brakes and the stock MC was fine. I upgraded to ‘95 twin piston calipers (D35 swap mainly) and whoosh... nobody home. So I went to a ‘85 full-size MC and all was well.

lvwill · Aug 11, 2019

When I swapped the rear to disk brakes I also installed the master cylinder for a 97 explorer. Rear disk brakes require more fluid flow than drum brakes. This was on a 92 ranger 4x4. The only thing I had to alter is shortening the pushrod on the booster.

Disc/Disc Master Cylinder for Bronco II

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