Technical Drum brakes - lack of stopping power

Squirrel, you're right, in a drum brake car the brake fluid pressure and volume to the front and rear wheel cylinders is the same, to make the front drums lock up first the wheel cylinder sizes front to rear are "juggled" to get more braking power in the front, on a disk brake car the front disks require far more volume than the rear drums hence the need for a "stepped bore" master cylinder. In other words the OP needs to change the master cylinder from disk/drum to drum/drum.

 

https://www.autozone.com/brakes-and...st-new-brake-master-cylinder-nm1614/49319_0_0

Master cylinder used by OP.

 

Most disc drum masters are not step bore…it will work fine, he doesn’t need to start changing parts until he actually figures out what’s wrong. As has already been said he needs to check the rear wheel cylinders.

 

Post # 53 jogged the mem. banks from while working as a dismantler, I recall thinking 'Clips? how crappy is this?'
" The General's methods have become..... unsound." Certain stuff should be discarded & dismissed for future use in this theatre. Taking a 'brake' now to peruse another thread regarding differences between pedal effort & hydraulic pressure. Selah.

 

Mustang master cylinders have a suttle valve and if it gets stuck in one position you'll have 2 brakes instead of 4.

 

I would like to see some sort of picture or documentation of this valve.

 

How did 1000 psi of pressure get to the rear if a shuttle valve could shuttle valve?

 

I'm thinking it could Chuck wood.

 

To add to 4 pages of input, nobody asked the OP if he had matched components?

 

OK, I'll ask....
Hey OP... do you have matched components??
There, now let the next 4 pages begin!

 

PDWL/Shuttle Valve - What is it?
The Shuttle Valve is a common valve in hydraulics systems where you can have 2 lines and if one line looses pressure, a "shuttle" plunger moves over and blocks the depressurized line. It makes it so that all your brake fluid doesn't squirt out onto the concrete if you tear a brake line. Car manufacturers use this feature to keep at least HALF (front or back) of your brake system working in a catastrophic leak. It makes a "2 circuit" system possible. So, deleting it just makes you go back to a 1 line system...and risks your brakes going out. Not great. It's worth having, and not that difficult. Land Rovers have them...

 

Do you have ANY clue how brake systems are designed?
Since the OP mentioned 79 Malibu, the front Calipers are 2.5" Rear bores are 7/8" and MC varies depending on power vs. manual. 7/8" manual vs 24mm Power. He has just slapped random components together hoping they would work. @Moriarity and others clued him in on other issues with his A body parts

Many of us keep actual reference materials on hand, in my case the Wagner brake bible and know how to use it.

 

So a pressure differential valve…not in the master cylinder as someone else eluded too. I’m not familiar with Land Rovers but so far no one has been able to supply me with actual factory service information that says one actually blocks fluid flow. Kinda defeats the purpose of having a tandem master cylinder No?

And they are absolutely not necessary to have a two circuit system

 

I'm sure more than just land Roger uses them.... I don't.....lol. Just explaining what they are.... And I agree with you

 

If the actuator rod is adjusted wrong the dual ports may not allow fluid to front and back brakes

 

What actuator rod are you talking about? The brake pedal pushrod? There is no “valve” inside of the master you have pictured. Lots of things don’t work if they aren’t put together properly.

 

The brake pedal pushrod I'm done, you can go figure and help fix his proble. I'm livin' the roadster life 12 months a year here in So Cal and you are freezing.

 

I was just trying to clarify your claim of a valve that was in the master cylinder.

Enjoy driving your roadster.

 

I’m not really sure either Mark, apparently I’m supposed to be jealous of his choice of location? I’m quite happy where I live.

 

If you are interested in the specs, I provided them on post number 75. It has drum brakes front and rear BTW. I had no idea this thread would make it to 4 pages. I have received some excellent advise, and as soon as I have some free time to work on the car I will put it to good use.

 

Izzat another way to say "chill"?

 

Read the specs I posted. You are so far off from the original application it isn't even funny.

 

Hey, re-read your comment above "To add 4 pages..."
I was responding to YOUR post, and you come back all snarky! ?!

 

And, please report back with the results. I'm sitting on the edge of my white porcelain seat here.

 

^^^^^ Best you sit back a bit. Just say’n.

 

My Model A Coupe stops GREAT with '41 Ford Front Brakes & 8" Ford Rear Drum Brakes....

 

And, what master cylinder are you using? Not being sarcastic, I really want to know. I've got '48 fronts, '70 8 inch rears and a '48 master cylinder.

 

Before you replace wheel cylinders make sure the rocking isn't just mounting screws being too long and bottoming out in the mounting holes! I've had wheel cylinders purchased new that weren't D&T deep enough and did this also. You can put a washer under the bolt head and tighten it down, and se if they're tight after doing that. If they are you can leave the washers in, or grind the length of the bolts down to work without washers.