Technical trouble getting my brakes dialed in

What do you have for brakes?
I have 1940 Lincoln re-pops on the front and standard Ford 9" out back. The front rear cylinders are an inch and 1/8, the rear wheel and cylinders are 7/8. I have a 1-in manual master cylinder with a 5 and 1/2 one ratio pedal arm.
I talked to the guys who make the repro Lincoln brakes and they said that setup should be fine, but it takes so much volume of fluid to get those brakes hard, the back ones fill faster than the front. As a result, my pedal doesn't get really hard until about 2/3 the way or 3/4 of the way through its stroke, relatively close to the floor. I've gotten used to driving it like that, but there's got to be a way to make it get hard higher.

I've considered a few options-
A larger master cylinder, or smaller wheel cylinders up front.
What say you?

 

Put a larger diameter master cylinder on the car, but that will increase the pedal pressure.

 

Are you sure that the volume that’s being used isn’t due to shoes not being adjusted properly?

 

With that stuff the pedal should be high with proper adjustment.

Is the pedal, pivot pin, and the master cylinder mount rigid with no flex?

Is the pushrod adjusted so there is only a little clearance to the master cylinder piston? I think it is better to "feel" that at the pushrod instead of the pedal pad.

Is the top anchor pin adjusted to center the shoes on the front brakes?

Try adjusting the brakes as tight as you can and then back off until they turn with a little drag and see if that helps.

Did you leave the self-adjusting stuff on the rear and if so how did you do the initial adjustment?

New shoes usually need several adjustments as they wear to match the drums.

 

I have the same setup front and rear that you do, my master cylinder is a mustang drum - drum and the pedals are genuine 1932 Ford modified for hydraulic brakes. Did you follow the instructions with the Boling Bros kit to set the top anchor up correctly? You have to leave it loose, apply the brakes and hold them while torquing it down then adjust the star wheel, this will center the shoes. Mine have been excellent. I would exhaust the adjustment procedure before replacing anything.

 

A couple little blue pills added to the master cylinder . . ?

 

If like original Ford on front 39-40
Brakes , to adjust you hang /apply 30 pound weight on brake pedal , adjust the front shoes, to center in the drum radius, Sometimes brake shoe arching required , two adjustments per Wheel

 

Yes, the shoes are out and making contact with no pedal

 

Check on all counts. Everything is set up properly, checked and re-checked.

Main issues; The brakes work, just not ideal - takes a lot of travel to.get hard. First inch and a half of pedal travel doesn't do much. The rear catches before the front and emergency stops are not as rapid as I would expect.

 

I did not do the centering procedure - will certainly try that. It's as simple as you describe?

 

I had a similar issue with my 46 ford stock brakes that are on my coupe. Very frustrating trying to bleed. I ended up putting on residual pressure valves. And adjusting the push rod pin made a big difference.

 

Yes, but I looked up the instructions and had one step backwards, the star wheel needs to be maxed out with the anchor loose, not the hydraulic brakes. My apologies, it has been over a year since I installed them. Here are the official instructions, see step 8.

https://cdn11.bigcommerce.com/s-fem...96.522605215.1547827472-1281480359.1540836783

 

Contact not good enough.

This is what I wanted to know. Now let’s see after proper adjustment is made when the entire shoe surface makes proper contact. You’ll be amazed.

 

That’s how I did it. Loosen the nut on the anchor, spread the star wheel link as far as possible to make the shoes have full contact, then tighten the anchor up. Loosen the lower link till you just get a hint of contact swipe when you spin. Press the pedal a few times and readjust the lower link to optimize the shoes as close to the drums without touching.

 

Adjusting the push rod pin? How so?

 

Mine has a deep female end on the clevis, and i added some all thread when I put in the new crossmember.

 

You need to have about 1/16” play between the end of the master push rod and the cylinder. This assures the master will retract all the way and allow the cylinder to refill with fluid every time. Also makes sure you aren’t having pressure against the wheel cylinders when the brakes are released.

You do have a brake pedal return spring to keep it up tight to the bottom of the floor when your foot is off, right?

 

As said, you've missed adjustment somewhere. It seems you have some instructions to get it right now.
I will mention something I've said before, for you and others who might read this later.
If you have a brake issue that you can't isolate, break it down to separate parts, just like wiring. In this case, you can block off the outlet from the MC to start and make sure the pedal, pushrod and MC are not the cause of excessive travel. Then block off the front, then the rear.
Try each part separately. It can be as simple as a brake line that's pinched off. It isn't going to be a permanent part of the system, just a test piece. It will usually show which end of the car has the issue.
Yes, it's messy. You will have to bleed each time. But it will show where the problem is.

 

I still don't follow what you mean by "adjusting the pushrod". I calculated the geometry in CAD and then made the parts - I have a rod with lathe-turned threads on one end and a bull-nose on the other. I have it adjust so there's practically no slop between the master, the rod and the pedal when at rest. Is that what you mean by "adjust" ?

 

What he means is have 1/16” to 1/8” free space between the bull nose end and the master when the brakes are off.

 

The pushrod they are discussing is located between the master cylinder and the power brake booster..

 

You don’t want no slop, you want 1/16” of slop. And you want a spring on the pedal so the weight of the pedal doesn’t push the pushrod until your foot is on it.

Get under the car and see if you can pull the pedal down a bit before the pushrod gets tight in the master. If you can’t, you might be putting pressure into the system even with the pedal at rest.

 

I've always worked on the clearance being something that you can just barely detect by hand rather than a measurable. This has stood me well for 50 years of messing with this stuff, despite not making any allowance for the possibility of differential expansion from exhaust heat.

Unclear to me that you've revisited the drum adjustment before getting diverted into a master adjustment?

Chris

 

Power brake booster ?

 

The weight of the pedal does not compress the MC at all. I designed it in CAD and the weight of the pedal and pad is well balanced as to not push. The pedal arm is against the steel toe board underneath, so it's not possible for the pedal's rod (I'm doing on one end and a bull nose on the other) to pull out of the MC. No springs on anything. Pedal returns to neutral position after letting off.

 

That's what I still have to do...adjust the bolt/pins on the top of those front Lincoln repro drums. It got cold AF here and I don't have a heated garage, so I'm eagerly awaiting spring.

 

Sorry just trying to tell you how it’s been done since 1939. Didn’t realize you used CAD to design the perfectly balanced pedal that has exactly no slop, but still doesn’t push the inner cylinder a little.

 

My MC, mounts and brakes are quite different from a anything 1939. The mount is Kiwi Konnection, the pedal is my design, the MC is an aftermarket unit (maybe an old Corvette copy), 10 lbs. residual valves in both lines, aftermarket Lincoln juice repros front and ford drums rear.

Sounds crazy, but it also has an MC designed for manual, all drum brakes, so the return is heavy - lots of shoe springs pushing fluid back. In addition, the pedal is only 5.5:1, so the pedal/pad weight has less leverage on the piston at rest.

When setting it up, I detached the push-rod from the pedal and slowly pushed it in to engage with the MC piston (no compression of the MC, just touching the bottom-out point of the bore in the piston - then marked the push-rod even with the back of the MC with a Sharpie. When I re-attached the pedal arm, the mark was still even with rear of the MC - the weight of the pedal does not compress the MC at all. It's not exactly no slop, that would be a bad move. I have the push-rod adjusted so I can pull the pedal up about 1/10 to 1/8" until it hits the underside of the toe-board. This keeps the push-rod from being physically able to pull out of the MC piston bore.

 

Put a spring on your pedal return even a temporary one and try your adjustment again. Gary

 

First of all the wheel cylinders should be a always full the valium will change as the piston move. My question are the hoses good a swelling hose could cause your issue.