Technical Whats the thoughts on a duel res. master cylinder?

So I'm building a single seater with no parts newer than 1950. I'm needing to start figuring out pedal location so I need to get a master cylinder. I'm using 40 ford front and rear brakes so I could use the 40 master cylinder but I'm thinking even though its not older than 1950 I should use a duel res. master. Whats your thoughts, Keep it period correct or make a concession for safety and run a duel.

 

what does a dual master cylinder do to improve safety? Does it actually make things better, or does it merely cover up for lack of maintenance?

Think about that....

 

I ran an original master in my 47 coupe and never had a problem. Just thought with the inferior stock replacement parts for old fords a duel master would have two circuits for stopping. What kind of maintenance do you do for a master?

 

Traditional is great, but IMHO it can be carried too far. After driving cars now for about 65 years and owning them with all sorts of brakes from mechanical to present day ABS systems on OT DDs, my opinion is that the dual master cylinder is the greatest single advance in automotive braking systems.
Some say that the move to hydraulic was the biggest advance, but my rebuttal is that when you had mechanical brakes, you knew they were not so good and you drove accordingly, allowing more room to stop, etc.
But when you had hydraulics, you were confident you plenty of brakes and maybe crowded things a bit, and then when a wheel cylinder blew, all of a sudden you had nothing!! With thje dual cylinder, at least you have 2 wheels with brakes.

 

K.I.S.S. ! A single works just fine in your case. Don't over engineer it. If your really worried about total brake failure due to the Master install an Old period correct E-Brake handle and make it work correct. If your going to say "PERIOD CORRECT" then be period correct.
The Wizzard

 

Period correct. It will look right, and if it, or a line ever fails, you might have a period correct wreck. No skid marks....

 

Now that's funny, I don't care who you are!

 

No skid marks is good. Means all the Brake system force is being used to slow down the tires. Skid marks mean your wheels are locked up and your sliding out of control and NOT slowing down very well.
The Wizzard

 

As I see it, the purpose of a dual master cylinder is to give you some "back up" in case there is a failure in the brake system. Brake system failures are not very common, but they do happen, and the results can be tragic.

So...how do you prevent brake system failures? Proper design and build is the key, but they also need maintenance. And if you don't have that second hydraulic circuit, make damn sure you have a good working hand brake (emergency brake).

If a dual brake system were necessary to survive, none of us over the age of 50 would be here to talk about it.

 

I'd say it's not a have to to have a dual master, but it's more like an insurance policy you hope you never have to use. Parts do fail, even new parts, and there is always the possibility of running over something and not knowing it broke off a brake line. Do you want that extra bit of insurance just in case something happens, or are you the kind of person that says, "I'll deal with it then if it ever happens."? For the minimal price and visual difference, I'll take the extra insurance myself. Squirrel's recommendation of having a working manual handbrake is a good thing to have, too. Just a little more extra insurance in case " Mayhem " strikes.
Like they used to drill into our heads during safety meetings at a job I used to have, "You can't be too safe, and you can't predict the impossible to predict."

 

you can look at it the other way, too. No matter how safe you make the car, things can still happen, and you could die.

99.9% (a number I pulled out of my hat) of cars on the road have dual master cylinders, yet 40,000+ people die on our roads every year.

A dual master cylinder does not make a car go from unsafe to safe. It just changes the odds a little bit, IF it's properly installed.

 

1964, a period correct story. I was a college dropout pumping gas on a corner Jenney station. The owners pride and joy was a 1956 ford 1/2 ton pickup, with the traditional business lettering on the door. It was regularly serviced and washed.

When I returned from a jump start call, the brake petal went straight to the floor as I set the parking brake. The front rubber brake line hit the rim in a sharp turn and a notch was worn into the line, it blew out.

The previous application of the brakes was for a line of kindergarten students in a crosswalk. 54 years later, I still am thankful for what did not happen.

I have witnessed a few single circuit brake failures since - fortunately, none involving damage.

When I bought my 1962 Volvo (marginally on topic), it had a front disk brake conversion (pre 1965 rotor and calipers). Visual inspection showed fresh, good looking stainless steel flex hoses. I did not jack it up and check the clearances from lock-to-lock. Fortunately, I was entering my driveway when I ripped an end off of a front brake hose.

It now has a Wilwood remote fill dual master cylinder (and new front brake hoses (and double checked the routing)).

 

Squirrel: Everyone I know that drove in the days of the single reservoir master cylinder experienced at least one complete brake failure, and quite frankly, we all can't be maintenance idiots.
Rusty Rocket: You already know the answer, just think what's the worst thing that can happen, now imagine your wife, son or daughter driving the car.

 

I was driving on the stock single piston until one day it did fail. Luckily no was in front of me and was able to pull over and bring it to a stop. Got it home and changed it before driving it again. It was very unnerving to be on a runaway freight train and it's just my opinion but there is a reason why factory cars were switched to duel in mid sixties. Totally agree with squirrel's answer about it not being the cure all for accidents, but good insurance.

 

Every time your under the car or doing service peel the lower lip of the Rubber Boot on the master back just a bit and see if it's wet. That would mean Fluid bypass. Time to service the master. This would be a good thing to do no matter what Master you end up using.
The Wizzard

 

As mentioned earlier the "emergency brake", didn't call them that for nothing. Chevy trucks (90s to about 2007) were notorious for having the brake and gas lines rust/blow out at the most inopportune times. It happened to me on two occasions in two different trucks. The second time I had no brakes what so ever. Made it home during Christmas rush traffic, 20-30 miles using caution and the emergency brake. Stupid?- yes, cheaper than a tow?- yes, Do it again?- probably not but it was a hell of an adventure.

 

My only personal single-master failure was a brake line that was rusted and I had made a hard stop. If I had been up on the condition of the lines I would have avoided it. Most master failures I have seen were the bypassing type, no fluid loss and the next pump stopped the car. Total master failures I've seen have all been when bleeding brakes.

 

I have a 2005 Chev truck that lost a brake line to rust above the gas tank that was not in an easy place to inspect. I had enough brake to get home. The brakes were deteriorating as the fluid exited the system. The truck was hauled to the garage rather than risk injuring someone to save a buck. The new lines are now all stainless steel. Having the brakes split front and back gave me the heads up that the brakes were failing when the pedal went too far. If a dual master can be installed w/o much fuss then it would be a reasonable thing to do. Old cars don't have much in the way of crash protection so having reliable brakes is reasonable.

 

cool stories...now we know why they went to dual master cylinders in 1967.

I risked it all this morning...took my old truck for another drive on the public roads. I made it home ok, this time.

 

Dual, no brainer. Unless you're making a museum piece, show car or recreating traditional, period correct road conditions. Too many things to go wrong on today's highways.

Last summer, I was driving a gift '65 Mustaang from my aunt. I'd only put about 100 miles on it since the mechanicals were gone over by a very good mechanic before she gave it to me. Drove 3 miles form home, pulled into the evening's cruise in and NO BRAKES. Fortunately, I was just creeping and grabbed the e-brake. It was an interesting ride home through the countryside. The MC reservoir was dry. Turned out, one of the front wheel flex hoses was a bit loose and leaked fluid each time the pedal was pushed. But, it never leaked onto the garage floor. Sure, I look at the engine regularly, but the reservoir is not see-through and who would have thought? Bottom line, a $75 retrofit '67 dual MC looks period correct and is a lot safer.

Your car, your choice. But, if we're sharing a highway, please keep your single jar car in front of me where I can keep an eye on you and not have you rear-end me in case our luck is bad.

 

I put dual master cylinders in all my cars......... and seat belts

 

We've all seen that scene in a movie, where an attempt is made on someone's life by messing with their brake lines.

I'm still waiting for the movie where the driver calmly downshifts through fourth-third-second-first, kills the ignition, and pulls up the handbrake, leaving the car neatly parked at the side of the road.

That said, I like a bit of redundancy.

 

In the movies, the brakes never actually quit working until the car is headed down a winding mountain road.

 

Nobody will see it if its under the floor. I don't think anyone would give you a hard time about having the dual master cylinder. I'm only 63, not like some of you old farts, but I drove a few old junkers when I wore a younger man's clothes, and I did have a few brake failures. None were wrecks, just nervous moments.
On almost the same note, how many have had the rag joint fail on their steering column? I have never had it happen and have never known it to happen to anyone else either, until mine failed in my 63 F100 ( with 65 chassis under it). A couple of weeks ago, I had my heart in my mouth when I was going down a road at 50 mph, when I suddenly had almost no feedback in my steering. I managed to limp it home, a couple miles away, with only a bit of friction holding the rag joint together. That isn't very common either, but it did happen. Almost had a heart attack.

 

Sounds like any of us over 64 must just be Dang Lucky to still be alive. How did we ever manage? L.O.L.

 

Have yet to have a dual reservoir stop me with a line failure.
Thank God for a working emergency brake.
Thank God no one was coming.

 

I’m all about period correct until it comes to steering and stopping i like the back up on the duel master.

 

Well, I missed Viet Nam (if you were in the service, thank you) and any number of close calls, some were even not my fault. Quite a few, oh, crap, moments. Guess I am lucky, indeed, to be 69.

 

I agree. Like I said above, it's just a little extra insurance. Things can and will happen, anything that improves your odds is always in your favor. I've driven old log trucks with a single pot and had the brakes go out while I was loaded, not a fun feeling. Had to scrub a few trees and clean out a ditch or two. Not something you'd want to do with a nice vehicle. Not saying it will happen every time, but if it does, anything extra is good to have.

 

With a little brain power, you can run a pair of single stage master cylinders, side by side.