DUAL MASTER CYLINDERS ....... THE BIG MYTH?

I wouldn't blame anyone for using a single M/C on an existing setup, but I don't see a reason to plan a new brake setup around a single chamber M/C.

I once had a rear brake line blow on my dual M/C car. Once one end of the system fails, you DO feel it, and it's scary. I never saw it coming. I was able to stop with the remaining brake power and the handbrake.

Dual M/C are cheap and easy to come by, why not use one?

 

Certainly hope you don't take this personally. You can run any braking system you are comfortable with. You know how you drive and how you maintain your car, I do not. But I know how I drive and how I maintain my car, for me, a dual master and at least front disc brakes are the way I will go.

It equally burns my butt when some people will ignore some safty issues simply because something is not "triditional". Few people I know will maintain a vehical to high standards, unfortunately those are the same ones that drive the 4 wheel disc, anti lock, computer controled rides Mon - Fri then jump into their hot rod on the weekend and expect the same braking results. Maybe I too fall into that catorgory, I remember the excitement of a total brake failure. It was probably because of poor maintenance, I was young and broke (as apposed to being old and broke now). So I guess I need to protect myself from me, and I am certainly not alone in that area. I do and will continue to suggest to people to invest in a dual master/disc brake set up. I would much rather error on the side of more safety. I think to suggest to the average population that a single master and drum brakes are the safest way to do brakes is irresponsible. But I do not pretend to think dual/disc are the only way to have safe brakes or to think that dual/disc brakes are always safe. But many of the people we talk to simply have no experance of a single master with drum brakes and have no idea what to expect. Put these same people together with less then standard maintance and I think you can see where I'm coming from. Just my two cents. Gene

 

i had a 64 Malibu before with a single jar M/C and a 6cyl. i did a motor swap to a sbc 350 with a 400 tranny. i didn't redo the brakes. it was alot of white knuckle driving. i hated the feeling coming to a stop light wondering if it was going to stop.

with all the performance goodies we put into our motors. we should do the same to our brakes.

now the 58 Ford F100 that i'm building is going to have pwr brakes dual M/C with disc/drum brake system. also my 54 chevy i'm building is going to have the same set up.

no more white knuckle driving for me, traditonal or not...

 

Plus some brake problems people have is they don't set them up tight enough on drum brakes because I've noticed on my drum drum setup on my 60 that if I set the brakes up a little tight I have a great pedal and I don't have to do any pumping to stop. when I first built it I didn't set the brakes tight enought and I would always have to pump them to stop but about the same time I started working for a shop that the owners drove cars like mine and they showed me that on those early setups that you want them setup a little tight when they are new because the first few miles that you use the brakes they wear alot untill they get set in they're grove per say. I've had fairly good luck with my drum drum single reservoir setup on my 60 but I would like to change it to a dual master and a disc drum setup but for right now I'm going to just pust a chevelle dual mastercyl for drum drum on my car. I've had a few white knuckle rides before I also had to drive a 3/4 ton 66 chevy truck with a manual 4 speed tranny 20 mile to my house with no brakes because I couldn't find anyone with a big enough trailer and I didn't have the cash to hire it done. Now that was a very slow and scary ride.

 

There May not be an answer to this question -BUT you can bet that if the single chamber master worked as good as the dual ,the OEM auto makers would be all over it -[using a single] to save 5 cents on each car!

 

Yeah, there's no need for a single reservoir system if you maintain your brakes very well--check the lines, etc. Mainly because rubber seals NEVER fail, and things never go wrong if you're on top of it all the time. And if you're using all new parts, then it's just about garaunteed that you'll be just fine, because nobody has ever bought anything new and had it fail after a little while or driving--like a water pump, a starter or whatever.
Wanna buy a bridge while we're at it?

I had a single reservoir fail on me once--no warning, no spongy pedal, no nothing--just came to a stop sign one morning when I was going to work real early, and I always start brakeing WAY before I need to, no matter what I drive. Pedal went down, car started to slow down, pedal stopped travel, car was still slowing, pedal instantly went all the way to the floor, and I'll swear to my dying day that the car actually PICKED UP speed! Jammed the old 3-spd behind the Nailhead into Second, ground it into First, litterally came up out of the seat and STOOD on the e-brake pedal, and managed to bring it to a halt--dead square in the middle of the intersection's Second lane, where I would have been crushed by a semi truck on the passenger door if this had happened at 9:00am when I usually went to work instead of 6:30am like I was that day. The road I blew through was the main state highway in Lakeland, Florida that the Publix grocery store chain is headquartered on, and their warehouses are all down that road, so there is a steady flow of truck traffic all day.
Someone was watching out for me.

As for the drums/disc discussion, my feeling on that is that if the drums are WELL ADJUSTED, then they should be pretty good. Not great, but okay in a heavy '50s car (like my '54 in the above story). I think the key is installing a set of self-adjusters at all four wheels, like later cars had. In a light hot rod, I think well-adjusted drums would be fine.
The problem is that we don't go out and adjust the brakes every 150-200 miles, so they aren't as tight as they should be, contributing to longer braking distances.

Brake fade is more of an issue with drums, but I think you could do pretty well with finned aluminum. I'm gonna convert my '54 to self-adjust, 4-wheel finned aluminum drums. It already has a dual reservoir.

Okay, off the high-horse now!
-Brad

 

I can recall that back in the 50's there were so many
leaking brake systems, (due to the use of single master
cylinders and drum brakes) that there was a river of
brake fluid running in the gutters of the streets of
our neiborhoods.
My dad had a gas station back then, and would buy 50
gallon drums of the stuff, just to keep up with the
demand.

See back then everybody drove with barely no brakes
or none at all.
If you really had to stop, you would just use the
the emergency brake. It was the only brake system that
you could depend on.

Well, this guy named Ralf came along and convinced
the people that Corvairs were unsafe for the reason
that they had single master cylinders.Thousands upon
thousands of people were dying and killing others
because of this brake system.

The proof was on the sides of the roads.There were
little white crosses everywhere.
Right before and after the Burma Shave signs.

LA to Vegas.... it looked like a white pickett fence.

So Big Brother stepped in and put an end to all
this highway killing. The Corvair was gone and soon
to follow were all cars that had this old brake system.

The "Dual System" was in place now and the
crosses soon disappered from the highways.
Our roads and neiborhoods are now safe at last.


Remember when Anti Locks first came out.....
People were crashing the shit out of those cars! Ha! Ha!


-----------------------------------------------------------
"Drive Hard...Die Free"
"Vagabonds CC"

 

The Corvairs had dual masters 1967-69. The U.S. Gov mandated dual master cyls for 1967. They were first on Ramblers (about 1962 or so) and optional for '65 vettes.

 

Bumping this to the top. It’s got some good stories of guys loosing brakes, with the amount of brake talk on the hamb lately.

there was a thread the other day of a guy putting disk brakes on a single MC. And a few others saying they done the same without issues. I think this is crazy and these stories above prove the point.

also in my Wilwood instructions it stated “must be able to bottom out the pedal with no fluid in the MC” one guy stated that above and it’s important

 

Single cylinder disc/drum, no proportion valve. Stops on a dime

 

Kinda like driving around with the mini spare tire full time.

 

Until it doesn't. Another vote for a dual master.

 

I’d be turning the tires on the rims pretty soon.

 

Yup, the reasons it’s on there now is that’s how dad built it back then. I’m probably going to go duel this time. Check my thread “blowing this thing apart”.

 

One of my early “stock” photos. Those tires are long gone

 

Your friend is giving you wrong information. Yes the dual master does have one piston, but the piston is two separate seals on one shaft, with two separate reservoirs. So if either fails, the other will give you some stopping power.
I never tested this until just a few weeks ago when one rear wheel cylinder failed as I was exiting the freeway and hit the brakes. The pedal dropped halfway and scared the heck out of me! I hit the brakes harder, and began downshifting, and got it stopped with front brakes.
So expect the car to take way longer to stop, but at least it will stop. I drove back home on the freeway about 10 miles, staying in the slow lane, and keeping huge distances between the cars ahead. I've always been sold on dual masters, and this just conformed my decision to use them.

 

Dual master cylinders have TWO pistons. Take one apart to find out for yourself.

 

Residual pressure valves go in the drum side of the system only. They are there to keep the rubber cups in the wheel cylinders expanded so the fluid doesn't leak away. Spring pressure keeps the shoes pulled away from the drums.

Discs do not use a residual pressure valve. They have no springs to pull the pads away from the drums. The only thing that pulls them away is the o-ring on the piston. When you push the pedal the caliper piston only travels a few thousandths to apply pressure to the pads. The o-ring does not travel in it's bore, just flexes enough to let the brakes apply. When you release the pedal pressure the disc system has to go back to zero pressure to let the o-ring relax and that pulls the piston back a few thousandths. Then any run out in the rotor or looseness in the bearings can move the pads back to the piston and away from the rotor. If you put a residual pressure valve on a disc system you will always have the pads tight against the rotor.

 

Residual valves prevent air entrance upon brake release, they don’t keep the fluid from leaking. Residual valves can be used with discs when the master is lower to keep fluid from running back to the master.

 

Some days I wonder why I even bothered to become an automotive engineer.

 

https://www.jalopyjournal.com/forum/threads/tech-week-57-fargos-brakes-101.1229211/

Read this, brakes simplified

 

Good article Fargo, slightly different than the information in my 1970 text books, but basically the same.
Mr. Gimpy, I'm wondering if you have ever made a post that didn't brag on your infinite wisdom and basically call everyone else in the world a moron. If so, I haven't seen it, which is why most of the time I just skip over anything you post.

 

If your brake pedal touches the floor/firewall when empty of fluid, then a dual master may not help you in the event of a line/single circuit failure. Cars are designed to use all of the pedal stroke, bottoming the travel inside of the master. If you swap in a dual circuit master into a car without enough pedal travel when empty, you will likely not be able to use the added safety built into the master. Having a great feeling pedal, and perfectly functioning brakes when full of fluid, doesn’t necessarily mean that when a problem occurs, that you will have the needed extra pedal travel to apply the working circuit as needed.

 

That’s pretty much my first year apprenticeship brake classes in condensed form!

 

You know that you can block my posts, right?

Also, if you believe that I am not making factual statement, you are free to post a substantive explanation as to why, and include the actual facts.

 

Dual master cylinders ?

I like this plan most. Mike

 

Where’s the twist handle to adjust during yellow flag laps…

 

No. 2lb residual can be used.

 

This gets two pages? You guys will argue about anything.

 

Yes, but it has to be a dug up 18-year-old thread!