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disc/disc Master cylinder

6

68angrypony

Member
What brake master cylinder should I use for a disc/disc brake set up on my 68 coupe? It appears they disc/drum with a 1inch bore, would that work? I am fine with a manual setup, but if I can get a pretty cheap power set up that would be great.
 
Not a bad way to go. If I can get something that just bolts right in that would be ideal. Like a manual disc/disc master cylinder.
 
"68angrypony" said:
Not a bad way to go. If I can get something that just bolts right in that would be ideal. Like a manual disc/disc master cylinder.
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I'm gonna bet that will be hard to find. By the time a disc/disc setup came along power brakes were pretty much standard, I would guess.

Bill
 
There are options out there that will bolt right up. Pretty standard mounting arrangement. Just have to get the right size bore that matches up with the pedal set-up (stroke) you have in the car to serve the needs of your brake system. 7/8" or 1" can both work in a manual system depending again on the stroke and desired pedal effort. With the right pieces manual braking is great and you don't need power assist.
 
Well I am using the 2012 mustang gt front and rear brakes. 13.2 front and I believe 11.75 rear. My car has 4 wheel drum currently and manual brake booster. Manual 4speed t-10 trans. Any recommendations?
 
"67 Fastback" said:
I read where a guy was using a fox body booster and a 96-up V6 mustang master. This has been my plan. I've got the parts, just haven't made it that far yet.
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That's pretty much what what I have... I used the same master cylinder both with the original PBR front calipers, 94-04 rear calipers I installed, and then again when I upgraded to the Cobra calipers with 13" front, ~11.5" rear rotors. It works fine for me. I think the v6 master is 15/16" bore.
 
is their pedal modification with that or can you just buy an adjustable rod and just put in the new booster/Master cylinder and adjust the rod and be good to go?
 
I know you stated you would be happy with manual brakes, and have gotten some fine suggestions. I'd strongly suggest sticking with that plan. If you want to use a booster you run into problems with the clutch linkage. The Ultrastang site is good reference stuff, as is Mustang Steve's website http://mustangsteve.com/.
 
You can get a grabber maverick disc/disc from rockauto.com for under $45, IIRC, it 15/16 bore. Its what i am running with my manual disc/disc setup.
 
"Fast68back" said:
You can get a grabber maverick disc/disc from rockauto.com for under $45, IIRC, it 15/16 bore. Its what i am running with my manual disc/disc setup.
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What year car would that be? How does the car stop/feel with that booster and disc brakes?
 
It looks like 74 was the year I picked for the maverick. I didn't see any of the choices for disc/disc. Do you have a part number? I only see disc/drum and then others that say Manual brakes with 15/16 bore but no further info.
 
I was running a 15/16 disc/disc manual MC for a long time but it always took extra effort to get the car to stop. I did some research and the larger bore actually does require more effort for less travel. A buddy was swapping to rear discs and I had heard about the 85 SVO manual MC. We ordered him a 13/16 for like $16, it's an aluminum housing, bolts in, but the lines are on the other side of the housing so it took some routing. He had more pedal travel but took less effort. I ended up swapping in the same for my car and noticed significant improvement in the braking.
 
It's not simply a matter of bore size. There is a balance between MC bore size and pedal ratio that determine the ultimate effort required and pedal travel. There is a ton of info out there to help understand it. Here is the first thing that popped up on a quick search. I have seen others that a specific to our cars as well.

http://www.airheart-brakes.com/pdfs/Mas ... ection.pdf

In many ways, it is a matter of personal preference. Simply stated, more force required equals shorter pedal travel. Less force, more travel.
 
An emphasis needs to be put on the caliper's piston size and how many are in each caliper. If multi piston calipers are used, then you need a larger reservoir. I would look serious at a 1 to 1 1/8" bore master cylinder say from a late 60's or 70's one ton Dodge truck. I would not go under a 1". Disc brakes require about 3 times more fluid to operate than wheel cylinders on drums. You don't want to have to push the pedal all the way to the floor to stop.

Here's the simple law of fluid transmission, it's called "Pascal's Law." Very easy to understand and all you need to do is use the numbers for both the caliper piston and the master cylinder piston and you can quickly see how changing these will effect a braking system. I would also recommend using a steel brake hose insted of the rubber ones. They will resist heat better and will not expand near as much as the rubber ones will. This gives a more firm feel in the pedal. One last thing is the brake pads. I personally like using a fairly cheap semi metallic pad for a street/strip daily driven car. IMO the best bang for the buck. If money is not an issue, then they are the full blown "Sintered" race pads that will give you better cold bite and withstand more heat than the semi metallic pads. I have never used them.

Here's a somewhat funny video that is a bit elementary, but at least explanes Pascal's Law right.
http://www.youtube.com/watch?v=VxLTDtaRCZk
 
Once you have the brake system installed and bled, it is a completely closed (filled) circuit. As the brakes are applied only a very small amount of fluid is needed to force the pads against the rotors. As the pads wear down is the only reason for concern in regards to reservoir size. If you monitor the fluid level over time it's not really an issue. Or am I missing something?
 
No, that's it, provided you check the fluid often. The only reason I mentioned it is if you have multiple pistons it doesn't take much wear for the reserve fluid to be used. It can easily sneak up on you.
 
I'm using 2012 mustang gt brakes front and rear. Fronts are dual piston and the rear are single piston. Why would I look at a dodge truck master cylinder instead of a mustang master with a 1"?
 
"68angrypony" said:
I'm using 2012 mustang gt brakes front and rear. Fronts are dual piston and the rear are single piston. Why would I look at a dodge truck master cylinder instead of a mustang master with a 1"?
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Forget what vehicle the MC was intended. It's all about the math as written above. Using the brakes and MC from the same car into yours sounds great but if your pedal ratio is different than the donor the system will not function as intended. This really isn't too complicated. There are only a couple key variables. The Maverick MC is a very good selection. It will do what you need. If you don't mind spending more, Wilwood units bolt right in and have large volume capabilities.

If you have doubts, (sounding like a broken record) call one of the guys who sells parts/kits to convert brakes on these cars. They will help steer you and even understand the principles.
 
Master cylinders are like trying on dresses for women. They will go through several before they fine the one that fits. What influenced "my choice" of using a Dodge MC was the fluid volume, ports on the outside where most of the late model Mustang face the engine and with the 1.125" bore and once on the car, it felt right (ratio's correct for me). One last thing to consider is installing an adjustable proportioning valve in the system. With this you should be able to "balance" any reasonable combo of you choose. Let us know what you use and how it works.
 
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