Thoughts on single reservoir, single piston master cylinders.

Ford, in 1966, had disc brakes on some of the full-size cars. They came standard on 7 Litre Galaxies, for one example, and used the old single master cylinder. Dual master cylinders came in 1967, mandated by Federal law. As pointed out here earlier, the switch that turns on the light indicating low brake system pressure is strictly a switch. It does not block fluid from leaving the system on the side that is leaking. There was an earlier thread, either here or on The Ford Barn, with a drawing of the FoMoCo version of the switch, which clearly showed it had no seals to isolate the leaking side. If your brake pedal goes to the floor, with a leak in either the front or rear systems, I would have to think the remaining system, is needing adjustment. I have had a failure in a dual system before, and still had some brake pedal left. Not much, and not enough to prevent a minor accident, but still some. There was a discussion on this subject on the 7 Litre yahoo group also, 3-4 years back. IMHO (H in this case meaning humble), the most well maintained single system, could suffer component failure, or have the system damaged in any number of ways.

 

Good information guys. Thank you to all that have commented. I believe this is an important issue and needs some light shed on it. Anyone else interested in adding something?

TTT

Hack

 

I used to run a single (Ford dump truck clutch master) cylinder for the brakes on my first roundy rounders in the early 1980's, with an adjustable proportioning valve.

It worked great. That is until one night when someone apparently pinched a brake line tying the car down on the trailer -- First lap at speed I hit the brakes going into turn one and promptly ran into the back of the car in front of me....HARD!

The next week I had a different brake system on the car.........

Al in TN

 

Seems like most everyone is pro dual, myself, im fine with both, ive been running a single master in my 34 truck for 10 years, in conjuction with an emergency brake, (not parking brake as they call them now) and have had no problems and am not worried about it in the least, in this posting your just hearing all the people piping up about the ones that have gone bad, how many havnt gone bad? when i build a car i go thru all the brakes, hoses, lines wheel cylinders and master, so its safe and i know its safe. and i make sure the emergency brake is in good working order too, and i arc all the shoes, then the emergency brake works great.

Ive had dual res masters go bad and you loose almost all of your braking, i blew a front line on my 98 chevy 3/4 truck, guess what, your front brakes do most of the braking so when you blow a front line there isnt much pedal left, and thats what happened here, i had less braking than my 34 e brake puts out. granted it was enough to barely stop my truck but thats what it was for.

a master no matter the type is only gonna work correctly if the rest of the brakes are up to par.

Theres always going to be the argument of whats better but my argument is of whats done correctly.

 

Well stated Titus. I agree totally. So now that there have been thoughts on both sides, I will tell you why I started this thread.

I am currently building a Model-A coupe and have installed a single NOS 59 Chrysler master on it. It is a new build so naturally all the parts, lines, hoses ect will be new.

I had one of my older hot rod buddies over one night and he took one look at the single master and said, " I demand that you change that to a duel at once! " Serious as a heart attack. He said that he had one fail on him at one point and was not too happy about it being on my chassis.

I told him of a time when I had a duel master on a 70 Buick I was woring on, fail outside of my shop. There were NO brakes at all and I nearly had an accident myself. So I am on the fence here. I will definately make the entire system safe and secure and will be installing an E brake, so I figure it will be ok.

I was more or less trying to bring good info to the board and keep our future builds and builders up to par with what we NEED TO KNOW. Thanks again to all who commented.

Hack

 

I lost the master in the fairlane about a month after a bought it years ago,I've never forgot that feeling of having the brake pedal go to the floor, dual master in all my rides and besides you all have your emergency brake hooked up anyway!!

 

Ah Ha . So prolly no one has a changed mind here ,it seems. You say 1967 was the first of the dual masters. My guardian angel was protecting me all those years that I drove those old cars and trucks. Good to know.

 

I'm with bodi, "here we go again". A few months ago there was a thread on this same topic. Most of the players in that one said that dual systems were bullshit and didn't work. When I opposed that I started getting beat up by them. I backed off as not to lower myself. I think single systems are good if well maintained, and dual systems are better (if well maintained). If I was starting from scratch it would definitely be dual. Ken

 

Glad you mentioned that, speedyb. I had forgotten about the one in my '64 Fairlane giving out in the driveway about a dozen years ago. Had the kids loaded up for a ride to school when that happened.

 

i lost a brake line once, a front line. i was four wheeling in deep mud, ran into a stump under the mud that snagged the brake line. i pinched it off with vice grips and limped my truck home by driving slowly and anticipating my stops. if it had happened suddenly on the road, i don't think my rears alone would have stopped me in a normal braking situation.
once a pedal goes to the floor, it takes several pumps to get the rest of the system to function enough to stop your vehicle. in an unaware, sudden brake loss situation, it doesn't matter if it's single or dual, more than likely, you'll be cruising through the intersection still pumping the pedal to build up the pressure.

 

I say if its not a concours car, a dual MC is the way to go. I had a single in my '60 Impala for years and never had a problem but for the rebuild I'm going with a dual. Not much more money but more peace of mind anyhow.

 

I drive a 4750 pound 66 T-bird with single pot and piston master cylinder. Car has power booster and factory 4 piston calipers and 11 inch drums, even has a factory pro portioning valve. Stops not too very well !! Needs a lot of leg to lock them up in a hurry, go with a dual master, just plain safer.


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There can be no argument that a dual is simply smarter and safer than a single master cylinder. That being said, I am running a single MC on my 27 and have for the past 25 years with (knock on wood) no problems so far.

Many years ago I had a 57 Pontiac and I lived on a steep hill. One morning I jumped in, put it in drive, released the emergency brake, and drove down the hill. Overnight the one wheel cylinder leaked all the fluid out and I had NO brakes. Luckily, I was able to turn it hard to the right and miss oncoming traffic at the intersection at the bottom of the hill.

So I do realize how duals are much safer, but I just make sure my brakes are maintained and that I leave a lot of stopping room when coming to a light or when traffic stops. Plus, I have a stickshift car, so I can downshift and shut off the key if I really had to.

Don

 

Running a single is a risk without a reward. There is no payoff.

 

List me along with the DO NOT use single bore / single reservoir master cyl folks.... Better ones (aka SAFER) ones are so easy to get, it makes sense to go safer.

4TTRUK

 

So does anyone know of a dual master cylinder that is a bolt on for a 39 ford brake pedal assembly ( under floor of course ) thanx Pete.

 

Single master cylinders should be banned.
So should drum brakes, cowl gas tanks, behind the seat gas tanks, under seat tanks, mechanical fuel pumps, carburetors, outdated safety glass, roadsters, Cabrolets, Pheatons, convertables, bias ply tires, inner tubes, tube era rims, fiberglass bodies, wood and steel bodies, old steel bodies, batwings, split wish bones, buggy springs, steel dashes, solid columns, wooden steering wheels, unpadded steering wheels, outdated power steering, old manual steering gears, car bodies without crumple zones, lap belts, unapproved and untested seats, Corvairs, steel chassis, straight axles, early IFS, unpadded gear shifts, dash knobs, radios, metal door and window handles, wind wings, steel bumpers, unauthorized wiring or vehicle modifications, V8s, straight 6's, bangers and all cars made before 1966.

Safety before style is the name of the game. A car should not be allowed on the road unless it has the same safety rating as the current year's Volvo.
That way as we zip down the freeway doing 80 on someone's ass, we will have piece of mind and can dedicate our time behind the wheel to talking on the cell phone, texting or surfing the net instead of worrying about actually driving.

 

No, it seems some of us have been there, done that and survived, and are willing to tell our experiences so other people can learn from our mistakes.

And as usual, there are some people who are just too smart and have all the answers, or too fucking stupid, to be able to learn from other people's mistakes.

-Brad

 

Well most on here are saying the dual is better and safer. Very few say a single shouldn't be run at all.
The thread was started by someone with a fresh build. He's asking about the pro's and con's of dual vs. single reservoir. There are no pro's to single. They don't do anything better than a dual, but the dual does do things better than a single.
Dual is safer and even the people who say when you crack the bleeder valve the pedal goes to the floor are forgetting that you can pump the brakes and get pressure to the side that's not blown out. Not as good as an uncompromised system, but you can stop. That's not true with single reservoir.
It's a little silly to run people down for supporting dual reservoirs. They are safer.
I've run single on quite a few rigs. Had problems but no disasters.
I have to replace nearly everything in my brakes on my car right now, so I'm going dual. It's just a safer option.

 

Just a comment to braking in general. I live in Alaska and brakes are about as good as downshifting a manual trans here-- and people do fine. It is dangerous but it just takes different thinking. If something jumps out at you, turning is your only option here because stopping wont happen brakes or not.

If you really want a single, go for it but drive knowing you might only have an e brake.

 

What about running two singles with a fabricated "T-bar" that activates both at once?

Just a thought I'd like to see some input on too..

 

This has been brought up 100 times over and will go back and forth until a mod closes the thread, Bottomline is a dual master cylinder is safer, Anyone who argues that is a dumbass and should not be working on their own or anyones car for that matter......It lets you keep some brakes when a line or wheel cylinder pops. But I don't see anything wrong with using a single pot if you have a good E brake, As that is what a E brake was designed for was in case your brakes failed. Seems some people forget they have a E brake and prolly would panic and never use it. Kinda like dipshits who are sliding on snow, If they would think! and let off that brake they could gain control of the car again. Now days a E brake is called a parking brake, because the daul master cylinder came along and gave us a backup. Anyhow this thread is going nowhere

 

That would be fine, But wouldn't it be easier just to run a dual master cylinder??

 

Yes, it would.. But some guys like the look of chromed out singles.

 

You guys in alaska don't count here in the states, As you are like super heros when it comes to stopping a car with little or No brakes. My brother in law, Has a guy from alaska who works for him, And last month we got 11 inches of snow here, And the mayor shut the city down and declared a state of emergecy. Jodie just laughed and drove his 2 wheel drive car with bald tires anywhere and everywhere he wanted to go. He called back home and had a good laugh with his family members up there, About how 11 inches of snow people panic and our mayor shuts the city down....LOL

 

I'm swapping my 58 ford from single to dual in the next month or so. I bought everything to do the swap for less than $75...not included the standard brake rebuild, just the dual res. conversion. Seems like cheap insurance especially when my kids will be in the car with me


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While we're on the subject, we're always told that dual-circuit master cylinder set-ups in our cars ought to be split front-rear and not diagonally as on new front-drive cars. Could one of the guys who know their onions give an explanation as to why this should be so?

Common sense would suggest that the imbalance resulting from having only one front brake and the opposite-side rear brake working should be more pronounced on a car with a large forward weight bias, like a modern front-drive car, than on a hot rod with near 50:50 weight distribution. The former would require more forward pressure apportioning, and hence result in greater pull to one side if one circuit fails, than in the latter case. So why no diagonal-split systems?

 

The rear brakes are smaller on most front drive vehicles (compared to rear drive) because, as you noted, the greater forward weight bias of FD vehicles. The problem was passing the DOT 105/135 partial systems stopping distance tests. With a vertical F/R split system, the small rear brakes were not able to meet the rear-only stopping distance requirements. Larger rears would have just added extra cost, weight and required much more proportioning during normal 4 wheel braking and other DOT test requirements. The solution was to tie one large front with one small diagonal rear. The result was very good DOT compliance with primary-only and secondary-only stopping distances virtually the same, along with reasonable vehicle handling. Note-there were/are large rear drive vehicles that originally had a vertical F/R system, but after being altered or stretched, overwhelmed the stock rear brakes, requiring the plumbing switch to diagonal.

The early FD vehicles during the '80s were sometimes a "handful" during partial systems testing, but over time suspension and steering improvements resulted in handling/stability very close, compared with full system and a partial primary or secondary system failure.

A good possibility of irregular handling and/or instability would be the concern with running a diagonal split brake system on a vehicle not designed for it while braking during a system failure. Power steering, at least, would be highly recommended!

IMO, it would be best to use normal rear drive brake components with a vertical F/R split on custom/modified rear drive vehicles.

 

The only problem with your theory is if you blow a rear wheel cylinder, and it hoses one of the drums with DOT3--I did that on my '54 Buick. No front brakes, and with the Emergency brake one of the drums was slick with DOT3, so I effectively only had ONE drum, to slow the 4,000 pound car from 40mph.

Even slamming the manual trans from 3rd to 2nd and then to 1st with the e-brake didn't get it stopped in time--and I was standing up out of my seat on the e-brake and shifted with no clutch. I blew through the intersection and came to stop in the far lane. (Particularly frightful, because I was coming to work early that day: had I come in at the regular time and that happened, I'd have blown through Hwy 92, with I-4 to my right and all the Publix grocery chain warehouses and bakery down to the left... at 6am, the road was empty; at 8am it's non-stop semi truck traffic.)

-Brad

 

I never said a E brake would stop you in any certain distance, But It is still better than no brakes!