What size master cylinder?

[Motorhead]

I'm wondering what size master cylinder to run on a non-power 4 wheel disc brakes setup? My truck has the Speedway GM disc conversion on the front axle and a Ford 8.8" rear axle (off of a late 90's Explorer). I won't be running a brake booster. I have a 1 inch "Corvette style" master cylinder and I'm wondering if it's sufficient.

Thanks in advance!

 

[sgtpontiac]

Just my opinion.....

I'm wondering what size master cylinder to run on a non-power 4 wheel disc brakes setup? My truck has the Speedway GM disc conversion on the front axle and a Ford 8.8" rear axle (off of a late 90's Explorer). I won't be running a brake booster. I have a 1 inch "Corvette style" master cylinder and I'm wondering if it's sufficient.

Thanks in advance!

1" bore is sufficent but you need to make sure the Reservoirs hold enough fluid.... when you say corvette style I assume you mean the one with the 2 D shaped Reservoirs of equal size? If so, it should be enough... but if it's one of the combos with one large and one small I would not use it....JMHO

 

[Motorhead]

Yes, it's a 'double D' master cylinder. I figured it'd be enough, but I thought I'd ask and see what other folks have used before.

The reason I asked is Speedway sells a 1-1/8" bore to be used along with a booster for 4WDB setup and 1" non-booster for disc/drum. I haven't seen anything in their catalog that is specifically advertised for use on a non-booster 4WDB setup.

Thanks again!

 

[sgtpontiac]

Are you using a manual adjust proportioning valve?

Just curious if you're using a manual proportioning valve? That way you can tailor the thing the way you want it.... a factory valve might not give you the control you want if the car is light or other things that differ from the style of vehicle you got if from..... JMHO

 

[Ol Blue]

The larger bore will need more pedal pressure than the smaller one. The volume of the reservoir isn't really an issue, since once the system is full and bled the fluid really doesn't move much, it's just under pressure or not. Iv'e read that the pedal ratio for non-power brakes should be 5-7 to 1. I made mine about 5 1/2 to 1 and I used a pinto 15/16 bore master with my disc/drum system.

 

[King Herald]

The larger bore will need more pedal pressure than the smaller one. The volume of the reservoir isn't really an issue, since once the system is full and bled the fluid really doesn't move much, it's just under pressure or not. Iv'e read that the pedal ratio for non-power brakes should be 5-7 to 1. I made mine about 5 1/2 to 1 and I used a pinto 15/16 bore master with my disc/drum system.

Good point. Check the brake fluid regularly and it should not be a problem.

I have ordered a 1" Speedway M/C for my project, which will have a disc brake converted 9" rear and some Jap disc brakes on the front.

I've allowed for leverage change by drilling four holes in the brake pedal.

You don't really want more pedal travel than you need, so I can adjust this to get the proper braking power, with the least pedal movement.

These holes are for decoration:

These are to change the mechanical advantage (leverage). And it rides on poly bushes, to keep it smooth:

 

[Got Rust?]

That look's good King Herald, thanx for the pic's

 

[King Herald]

I thought I'd come back to this, as I recently plumbed my brakes and was pretty frustrated to find they simply don't work properly. long story short, I have a disc/drum master cylinder and they do not move enough fluid for a disc/disc application.

I've spent four days messing about with it, reversing lines, bleeding, testing calipers. I even connected front and back circuits together to 'share' the fluid flow, but for some reason the pedal sinks down and fluid overflows the rear smaller reservoir, obviously being pushed through the system somehow.

My TH350 trans has a fault too, no reverse and some other strange things.

The car was all but ready for a test drive, and everything was going well, motor fired right up, all electrics worked, so now I'm pretty fed up with the whole thing.

 

[Old Iron]

KH, I went through the same thing..
I ended up using a Corvette master cylinder with both reservoirs being the same size. The front reservoir is for the front brakes and the rear is for the rear brakes.
If it's power brakes ? to get the correct pedal travel, I ended up drilling a hole 3/4" lower in the pedal arm. I now have great brakes on my 66 Chevy pickup.
I use this master cylinder on all the brake systems I do, Disk front drum rear and/or disk front disk rear.

 

[BigIrish]

I've used the standard Speedway master cylinder that comes with the Model A brake pedal kit on 3 rods now and it works perfectly. Its a late 70s Ford style with the front reservoir bigger than the back.

On all 3 cars I've used the Speedway disk brake kit and a Ford 8.8 with disk brakes. I've also lucked out that the system seems pretty balanced and doesn't really need the proportioning valve (but I have it).

It sounds to me like you have a partially defective master cylinder that allows fluid to flow between the chambers.

Also, do you have 2 psi residual pressure valves installed? Without them, too much fluid will drain back to the master and you won't be able to move all that fluid back into the calipers with one pedal stroke.

 

[Sumfuncomet]

Brake mc help

There are a lot of companies like Wilwood that have great tech sections on their websites. Also Longacre Racing is a good place to look