Brake master cylinder bore

[Zandoz]

I bought my pedal assembly a year or so ago. It came with a pair of master cylinders of unknown specs. With a bit of research I've been able to determine that they are both 5/8" bore. To me that seems small. They will not be boosted. The front master is likely to be used with the GM metric callipers that come with Speedway brake kits. The rear brakes are a bit of a question right now. The axle is from an '88 T-Bird Turbo Coupe that came from the factory with the same disc brakes as used on the high end Mustangs...but the callipers are gone and the rotors are scrap. I have gotten a nice pair of drilled and slotted rotors, but I still need callipers. I'll probably just go with Ford OEM callipers.

Now the big questions. Are the 5/8" bore masters sufficient for the front and rear brake configurations? If not, what size bore(s) would be best?

 

[fletcherson]

I bought my pedal assembly a year or so ago. It came with a pair of master cylinders of unknown specs. With a bit of research I've been able to determine that they are both 5/8" bore. To me that seems small. They will not be boosted. The front master is likely to be used with the GM metric callipers that come with Speedway brake kits. The rear brakes are a bit of a question right now. The axle is from an '88 T-Bird Turbo Coupe that came from the factory with the same disc brakes as used on the high end Mustangs...but the callipers are gone and the rotors are scrap. I have gotten a nice pair of drilled and slotted rotors, but I still need callipers. I'll probably just go with Ford OEM callipers.

Now the big questions. Are the 5/8" bore masters sufficient for the front and rear brake configurations? If not, what size bore(s) would be best?

That sounds small to me too, but you have two, one front, one rear. That likey makes a difference, effectively that seems it would be equivalent to a 1-1/4". The one I bought is 1", but is a standard ford mc. Can you access the manufacturers specs to get their recommendations? Perhaps look at wilwoods site to compare...

 

[choppedtop]

I think a 1" would be the correct size for for a dual master cyl. with 4 disc brakes. I have a dual m'c that is 1 1/8" for my drum/disc set up, but it take more for the drums. Not sure is 5/8 would give enough volume before running out of pedal travel.

 

[Zandoz]

That sounds small to me too, but you have two, one front, one rear. That likey makes a difference, effectively that seems it would be equivalent to a 1-1/4". The one I bought is 1", but is a standard ford mc. Can you access the manufacturers specs to get their recommendations? Perhaps look at wilwoods site to compare...

The masters are Tilton 74s, but so far I've not found any recommendations for what they would be applicable for. If they are not suitable, I'll be going with the Wilwood compact masters that are available all the way from 5/8" to 1-1/8" bore. They'd give me more wiggle room. But I've not found application recommendations for them either.

The more I think about it, what I'd really like to do is scrap the separate masters and pedal setup, and go with a single tandem remote reservoir master and pedal. That setup would give more interior pedal room. The problem is I've not been able to find a remote reservoir unit with right side outlets...except with you guessed it 5/8" bore.

 

[Zandoz]

I think a 1" would be the correct size for for a dual master cyl. with 4 disc brakes. I have a dual m'c that is 1 1/8" for my drum/disc set up, but it take more for the drums. Not sure is 5/8 would give enough volume before running out of pedal travel.

I don't have the conventional dual/tandem master setup, it's 2 separate masters...one for the front, one for the rear. When I got the pedal assembly and masters as seriously good package deal, I was mainly buying the pedal assembly, and the unidentified masters were a bonus.

 

[choppedtop]

Correction needed here Bill. My m/c is 1". It has side outlets, like you mentioned. Spirit supplied mine.
Lee

 

[Zandoz]

Correction needed here Bill. My m/c is 1". It has side outlets, like you mentioned. Spirit supplied mine.
Lee

Are the outlets on the right/passenger side? Is it a remote reservoir unit?

 

[choppedtop]

With the plunger facing toward the front, so that the brake rod would push it in, the outlets would face towards the passenger side. Take a look.
Dual Feed Master Cylinder for Manual Brakes, 1" Bore - Spirit Cars

 

[tnoftsger]

Check the math. Area of MC bore X Stroke is volume (PI*R^2*stroke)
Then that volume /Area of Caliper piston/2(2 calipers) = caliper piston movement

I don't think you going to get enough piston movement to get good brakes. Maybe just me.

 

[fluidfloyd]

The problem is I've not been able to find a remote reservoir unit with right side outlets...except with you guessed it 5/8" bore.

Bill...Here is a link to Wilwood. They have exactly what you're looking for. Hope this helps you out.
George

Wilwood High-Performance Disc Brakes - Master Cylinders

 

[fletcherson]

The masters are Tilton 74s, but so far I've not found any recommendations for what they would be applicable for. If they are not suitable, I'll be going with the Wilwood compact masters that are available all the way from 5/8" to 1-1/8" bore. They'd give me more wiggle room. But I've not found application recommendations for them either.

The more I think about it, what I'd really like to do is scrap the separate masters and pedal setup, and go with a single tandem remote reservoir master and pedal. That setup would give more interior pedal room. The problem is I've not been able to find a remote reservoir unit with right side outlets...except with you guessed it 5/8" bore.

Not sure why you need that, mine is under the floor and is a ford mc, like a older mustang with disc,drums. I am putting a door in the floor to access it. It's out of sight, out of mind. You can mount them wherever makes sence and make linkage to work it. Mine has the outlets on the left, and it mounts backwards, so it works out nice. Not too crowded to bend lines nicely.

 

[fordsbyjay]

So is this a new build then? I am not quite sure from your post if you have actually used the dual cyl setup yet or not so I will just share my experience.

Brake systems are all about pressure. Smaller bores require less effort to make the same amount of line pressure but will require longer pedal stroke. A longer pedal will also increase line pressure but in you case that is a fixed length. A hard pedal typically means you do not have enough line pressure and braking will be poor. Smaller than 5/8" could create an issue with not enough. If they are ok I would use them as is until you get some experience and then adjust from there. FYI, you can actually buy a brake pressure gauge and put it on the caliper (bleeder screw) and measure your line pressure.

Dual m/cyl typically require smaller bores than a standard tandem m/cyl. I have used a couple of them and I have 5/8" cyl in my 64 Falcon (Brembo 13" brakes).I don't understand why myself but I did have a 1" initially and the pedal was very hard and would barely stop the car. I talked to a brake engineer and he was the one to recommend the smaller m/cyls. I would call Wilwood if that is what you are looking at before believing anyone online (or at least someone that has plenty of experience with the dual m/cyl units).

To be honest I don't know how you are going to fit dual m/cyl down there because there is so little room already. I had to put a 90 on my tandem m/cyl to clear the th350 in my car.

In a typical tandem m/cyl I like the 15/16" 86 Ranger unit myself. They have a plastic reservoir which is easy to see when they are mounted under the car. The screw off cap is so much easier than trying to get those stupid wire clamps of the corvette m/cyl that everyone sells.


1986 FORD RANGER 2.3L 140cid L4 Master Cylinder | RockAuto

 

[Zandoz]

Bill...Here is a link to Wilwood. They have exactly what you're looking for. Hope this helps you out.
George

Wilwood High-Performance Disc Brakes - Master Cylinders

Yeah, I've practically lived on that site for the last week or so. They have what I need to continue with the dual master setup...a pair of the Compact Remote Combination Master Cylinders, with Banjo Outlets. When the time comes, I'd just get their recommendation on the bores needed, since it's pretty obvious the 5/8" bores I have will not be sufficient.

To go to a single tandem master, they have nothing that will work. A remote resevoir is a must because of an attached reservoir' proximity to the block and headers. Their only remote master has the outputs that point straight down, and would end up about a 1/2" above the frame...not enough to squeeze in banjo fittings.

 

[Zandoz]

Not sure why you need that, mine is under the floor and is a ford mc, like a older mustang with disc,drums. I am putting a door in the floor to access it. It's out of sight, out of mind. You can mount them wherever makes sence and make linkage to work it. Mine has the outlets on the left, and it mounts backwards, so it works out nice. Not too crowded to bend lines nicely.

One of my main guiding requirements for this build is that nothing goes under the floor that does not absolutely have to be there. With my mobility issues, anything under the floor will be totally inaccessible to me without removing the body. As much as possible I need everything accessible from a chair or wheelchair. I can not kneel to work through a hole in the floor...or get down low enough to work from the ground or a creeper.

Another guiding requirement is simplicity. If possible, I want to avoid custom bracketry, linkages, etc. With the floor mount pedal assembly I have...or the one I'd use if I can find a suitable tandem master...the only bracketry required would be 2 simple plates with some holes. The only linkage would be the pushrod(s) that come with the masters.

Plus, those two simple mounting plates will do double duty as floor and firewall supports.

 

[Zandoz]

So is this a new build then? I am not quite sure from your post if you have actually used the dual cyl setup yet or not so I will just share my experience.

Brake systems are all about pressure. Smaller bores require less effort to make the same amount of line pressure but will require longer pedal stroke. A longer pedal will also increase line pressure but in you case that is a fixed length. A hard pedal typically means you do not have enough line pressure and braking will be poor. Smaller than 5/8" could create an issue with not enough. If they are ok I would use them as is until you get some experience and then adjust from there. FYI, you can actually buy a brake pressure gauge and put it on the caliper (bleeder screw) and measure your line pressure.

Dual m/cyl typically require smaller bores than a standard tandem m/cyl. I have used a couple of them and I have 5/8" cyl in my 64 Falcon (Brembo 13" brakes).I don't understand why myself but I did have a 1" initially and the pedal was very hard and would barely stop the car. I talked to a brake engineer and he was the one to recommend the smaller m/cyls. I would call Wilwood if that is what you are looking at before believing anyone online (or at least someone that has plenty of experience with the dual m/cyl units).

To be honest I don't know how you are going to fit dual m/cyl down there because there is so little room already. I had to put a 90 on my tandem m/cyl to clear the th350 in my car.

In a typical tandem m/cyl I like the 15/16" 86 Ranger unit myself. They have a plastic reservoir which is easy to see when they are mounted under the car. The screw off cap is so much easier than trying to get those stupid wire clamps of the corvette m/cyl that everyone sells.


1986 FORD RANGER 2.3L 140cid L4 Master Cylinder | RockAuto

This is a new build...but a lot of the components are excellent condition used. The brake pedal assembly I have is one of those used components. The 5/8" Tilton masters came with the pedal assembly. I figured that if I could use them, great...if not, oh well. I personally have not used them...or any dual master setup. Yeah, space is a premium, even with a tandem master...but with remote reservoirs it is doable. The dual masters work because the outputs are straight out the ends. With a tandem master, banjo fittings would make the setup work, and even give me a bit of wiggle room...but right side outputs would be required.

 

[fordsbyjay]

I have a few dual pedal assemblies laying around the house so I took some measurements and a couple pictures.

Here is the 15/16" Ranger m/cyl I put in my tbucket next to a Tilton pedal assy I have. (ignore the clutch pedal) I understand your requirements of serviceability and I feel the same way. Typically there is a hole in the body floor with an access panel to the master cylinder. The clear reservoir allows visual inspection by just removing the simple access cover on the floor. Very simple to do and no crawling around. There should never be any reason to add fluid (other than flushes) but this can easily be done through the access hole.

Anyway, the Ranger m/cyl is about 4" wide and the dual m/cyl is 4 1/4" wide.



The Wilwood dual pedal assy.


Based on my experience the problem you are going to run into is the pedal itself. All brands are typically rather straight with a curve at the end where the foot pad is. I have found (especially in a floor mount setup) that it puts the foot pad in a very lousy position. Always to far back wasting valuable legroom. I found even the Total Perf. pedal in my car wasted a lot of space so I cut it in have and changed the angle to gain 4" more space.

You may be thinking "I will just move the pedal assy farther ahead" but here is no room because that is where the bellhousing is going to be.



They make tandem m/cyl with a remote reservoir which would allow you to use an standard off the shelf already made tbucket pedal assy yet have the serviceability you want.
Wilwood 260-7563, Wilwood Combination ''Remote'' Tandem Master Cylinder | Wilwood

Here is pedal assy I built years ago based off the Wilwood dimension. It illustrates what I mean by the foot pad being too far back ( closer to the driver) and it typically how it turns out.



I am not trying to sway you either way just point out some of the issues I have found over the years and offer alternatives that you may not have thought about.

Good luck.

 

[fletcherson]

I had the same issue when fitting pedals. The only place that made sence for me was under the floor. Other wise there was too much wasted space. I needed every fraction I could get. I was dealing with a clutch too, but the same space in question.

 

[Zandoz]

I have a few dual pedal assemblies laying around the house so I took some measurements and a couple pictures.

Here is the 15/16" Ranger m/cyl I put in my tbucket next to a Tilton pedal assy I have. (ignore the clutch pedal) I understand your requirements of serviceability and I feel the same way. Typically there is a hole in the body floor with an access panel to the master cylinder. The clear reservoir allows visual inspection by just removing the simple access cover on the floor. Very simple to do and no crawling around. There should never be any reason to add fluid (other than flushes) but this can easily be done through the access hole.

Anyway, the Ranger m/cyl is about 4" wide and the dual m/cyl is 4 1/4" wide.



The Wilwood dual pedal assy.


Based on my experience the problem you are going to run into is the pedal itself. All brands are typically rather straight with a curve at the end where the foot pad is. I have found (especially in a floor mount setup) that it puts the foot pad in a very lousy position. Always to far back wasting valuable legroom. I found even the Total Perf. pedal in my car wasted a lot of space so I cut it in have and changed the angle to gain 4" more space.

You may be thinking "I will just move the pedal assy farther ahead" but here is no room because that is where the bellhousing is going to be.



They make tandem m/cyl with a remote reservoir which would allow you to use an standard off the shelf already made tbucket pedal assy yet have the serviceability you want.
Wilwood 260-7563, Wilwood Combination ''Remote'' Tandem Master Cylinder | Wilwood

Here is pedal assy I built years ago based off the Wilwood dimension. It illustrates what I mean by the foot pad being too far back ( closer to the driver) and it typically how it turns out.



I am not trying to sway you either way just point out some of the issues I have found over the years and offer alternatives that you may not have thought about.

Good luck.

First off I want to thank you for going above and beyond to get pics, dimensions, etc.

If I were going with a firewall mounted pedal assembly, I'd be all over one of those Ranger masters....really neat, small, and not pricey. This is another one of those circumstances that I should have remembered those...I had an '85 Ranger for several years.

For my application master(s) with top mounted reservoir(s) just will not work. I've not been able to find a top reservoir M/C that results in more than a 1/4" clearance between the top of the reservoir(s) and the headers. For example, with the Wilwood masters I'll probably use, there's a 3" or so gain in clearance going with the remote reservoirs.

The reason these

will not work is that the floor mount pedal assembly, and therefore the master, would mount directly on top of the frame rail. Those down pointing outlets don't leave enough clearance with the frame rail to squeeze in banjo fittings...and regular elbows don't even come close.

The reason an under floor top reservoir or bottom outlet master will not work for me, besides accessibility and added complexity, is ground clearance. The bottom of the frame rail, in the neighborhood the master would live, is only around 6-1/2" above the ground...and I'm hoping to get that down to 6". That leaves only the 4" frame rail height to safely fit everything in.

This is the pedal assembly I have...part# 340-1285
Wilwood High-Performance Disc Brakes - Pedal No: 340-1285


The masters I'll probably use are the remote reservoir configuration of these...part # 260-136_ _ Wilwood High-Performance Disc Brakes - MasterCylinder No: 260-10372


They are a hair under 1-3/4" wide, and a hair over 3-3/8" long each. The total width of the combined pedal assembly mounted dual M/C footprint is only around 4-1/4" wide.

The 5/8" bore Tilton masters that came with the pedal assembly are about the same width, but about 2" longer. If the bores were sufficient, the additional length would not cause a problem.

 

[fordsbyjay]

This is the pedal assembly I have...part# 340-1285
Wilwood High-Performance Disc Brakes - Pedal No: 340-1285
View attachment 11865

This is the same unit I started with in my Pinto. The foot pad ended up way to close to the seat so I used the alum bracket and made a new steel pedal (shown in my last rusty pedal picture).

 

[Zandoz]

This is the same unit I started with in my Pinto. The foot pad ended up way to close to the seat so I used the alum bracket and made a new steel pedal (shown in my last rusty pedal picture).

Leg room is one of the few areas I'm not likely to have issues. The body is stretched 8-9"... and I'm only 5' 7", with legs shorter than typical for my height. Yes, I am a freak of nature...lol. Seriously...on paper using a made to fit plywood and webbing based seat, I'm coming just a couple inches shy of the legroom dimensions of our Buick LeSabre, with the seat full back. Of course the thickness and density of the cushioning will vary that dimension.