Technical Drum brake setup issues

I'm starting to go through the brakes on a project I recently purchased and am learning as I go.

The setup is a 1600lb model t bucket it has 1946-48 Ford hydraulic drums on the front (bore size 1 1/8"), the rear is from a late 90s Jeep with drums (bore size 13/16") and the master cylinder is a late 60s GM for drum/drum cars with a 1" bore. The front and rear each have an inline 10psi residual valve and there is a proportioning valve on the rear.

Would this size MC work well with those wheel cylinder bore sizes?

The few times I've driven it the brakes do stop the car but I feel like it should be better even if it is drums all around. The front shoes are worn and shiny but not worn down close to the rivets. Just wanted to get some insight before I start purchasing parts.

 

Get brake psi gage kit from summit for $50 and see where that cylinder psi is so you can insight and guess better.

 

These guys have been real helpful in the past.
Just give them a call
https://www.mpbrakes.com/?gclid=EAIaIQobChMIzNmf2ImV5gIVI4VaBR2UXwiyEAAYASAAEgJkJPD_BwE

Rich

 

Are you comparing stopping to a modern daily driver?

 

No I know not to expect that kind of braking perfromance. It just seems surprising I can't get any wheels to lock up in a stand on the pedal panic stop with skinny bias tires. I guess I can at least order new shoes for the front and see if that makes a difference. The drums look ok with not too severe grooving.

 

What's the shoe contact pattern look like? In other words, were shoe's arced then adjusted correctly?

 

You may not need the 10lb residual valves as they are probably in the master cylinder already if it's from a 60's drum/drum car.

 

The '39-'48 Lockheed non-servo (Ford) brakes used a dual-sized wheel cylinder, and 1 1/8"/1" would have been a rear cylinder. (Larger pistons contacts the forward shoes) Fronts used 1 1/4"/1" and 1 3/8"/1" depending on year, so are you sure you have Lockheeds? These brakes have to be assembled and adjusted correctly.
The 1'" master will work OK. What is your pedal ratio?

 

The shoe contact looked even across each shoe. I did notice this time the front shoe is more worn than the rear and is getting close to the rivets so I will definitely order new shoes.

I was wondering about that. Would the added inline residual valves cause a problem if there are already residual valves in the Mc?

Sorry I must have misread the wheel cylinder size somewhere else. These are 46-48 front ford brakes without the adjusting bolt at the bottom. Not sure if previous owner put the correct wheel cylinders in or not. They do look fairly new. My pedal ratio is 4.75 to 1 From the pad to the pivot is 9.5" and pivot to brake arm is 2" in case I didn't do the math right

 

I think your pedal ratio is lacking. 6-1 would be a big difference.


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I will try to re drill the brake arm mounting hole and see what happens.

 

If there is no booster than definitely try to increase the pedal ratio


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If you have a residual pressure valve in the cylinder, and then another in the line, it will not cause problems. ECI told me this. They are experts in braking systems, and they do make really nice residual valves out of brass, not cheap aluminum.

I think I'd try to find and fix the problem before you replace those nicely bedded in front shoes. Getting the proper arc on a set of shoes seems to be a big problem nowadays, and you know yours are already there. Replace them later when they have worn down too much.

 

I'd agree that pedal ratio probably has something to do with what you are experiencing.
I don't believe that the residual valves will affect the stopping power in the least. Their only purpose is to keep the lines full and keep that pressure against the cups of the wheel cylinders. I've got the same master cylinder in my 48 Chev with 54 Chev car wheel cylinders on the front and 75 Nova on the rear and while it is definitely a drum brake setup it stops pretty decent if the brakes are adjusted right and everything is up to snuff.
There is a big difference in the quality of brake lining for drum brakes and some does for sure stop better than others. I'd do some checking into and maybe someone will suggest what they see as the best lining for those brakes.
Years ago when I was often doing several brake jobs a day I found out that the super cheap lining was usually quieter and seldom had pulling issues when you hit the brakes but didn't stop as well or last near as long as the high quality lining that often could be a bit noisy and sometimes pulled if everything wasn't right on. The little old couples in town that drove maybe 4 k a year if that and normally didn't go past the Waco city limit signs but once or twice a year were real happy with those shoes but I didn't put them on younger guys performance cars..

 

T buckets

Just measure things up.
You’re going to need full stroke on the master with the available room for pedal travel. Might need to get creative in a T bucket. Real creative like adding a small booster further back.
Pics help.

 

4.75 pedal ratio and a 1" bore will provide just over 900psi with a 150lbs input, or just over 600lbs with 100lbs input.

I wondered about my input parameters as I'd no recollection of where I'd got those from. I seem to recall 200lbs being a benchmark, I think from some racecar source, which is possibly at the upper end of the scale. Did some searching and found this, interesting! 1970 research - The Brake Pedal Force Capability of Adult Females.

http://nvlpubs.nist.gov/nistpubs/Legacy/TN/nbstechnicalnote557.pdf

Admittedly relates to the fairer sex only. It mentions 200lbs as a standard, and states that over 50% of the sample couldn't achieve the 200lbs. That's girls for you!

Methinks, along with others, that the OP needs a better pedal ratio, or assistance. Maybe even a muscular girlfriend?

Chris

 

JFYI, D.O.T. brake test standard 105/75 for all U.S. vehicles was established in 1975, where 150 lbs pedal effort was the normal maximum allowed for all minimum stopping distance testing, and 200 lbs under .1/sec. was the minimum spike test requirement. Your input parameters may have come from this.
Additionally, 200 lbs minimum was also used for static testing brake pedal assembly and mounting integrity.

 

I'm going to have to get new shoes. When I took a closer look at them and cleared away the brake dust the front shoe is pretty close to the rivets so they don't have any life left.

Yea hopefully someone can chime in with some suggestions on quality shoe replacements. Using the search function people say they get them at Napa and posted Raybestos part numbers but when I search those numbers anywhere nothing comes up.

I don't have any good photos of the MC but a booster would be a tough fit. I will try changing the pedal ratio to make sure i'm getting a full stroke of the MC and see if that improves things.

Hopefully the increased pedal ratio will help. That will be a lot easier than making the girlfriend more muscular haha

 

Do not replace those warn shoes until you have your brake problem resolved!

 

I told him that but he didn't want to listen. Hopefully he has a way to perfectly arc them and adjust them so he doesn't introduce more issues before he finds the true problems.

 

IF you replace your brake shoes, make sure you get riveted lining and not bonded. Bonded shoes are usually hard and have poor friction capability. Also don't get your drums cut because the larger they get the more poorly the arc of the shoe fits. I sandblast my drums to knock the glaze off help the new shoes " wear in" . Also I gotta agree on the pedal ratio suggestions and will also say that Bendix brakes are FAR SUPERIOR to the Lockheed brakes you have on the front.

 

The front shoe is worn down to the rivets to wear the rivet is rubbing. I understand arching the shoes but obviously these shoes need to be replaced!

 

I will try to get some photos of the shoes up tonight.

 

This is the leading/front shoe you can see the material is worn down to the rivit


This is the trailibg/rear shoe not as bad but pretty worn.

Obviously I need new shoes. I will try to adjust the brake pedal ratio first to see if there is any improvement but I don't want to drive far and risk damaging the drum. I don't have a micrometer to measure the drums with. If I buy new shoes would it be best to buy new drums too or will they still not match and need arching?
Here is a photo of the drum brake surface

 

Thanks for the heads up on the shoes and drums. I assume the bendix brakes are the f100 swap. I looked into that but didn't want to have to buy even more stuff to do that conversion. I was hoping these would be enough for a 1600lb car

 

They work damn good when set up correctly. Post up a full side shot of brakes so we can see everything. I don't if it's been mentioned already but look at your wheel cylinders also. A freeze piston at one end can also cause one shoe to wear.

 

There is a better photo showing everything. I will try to get someone in the car tomorrow and hit the brakes do I can watch the wheel cylinder.

 

A friend of mine who isn't a car guy had the brakes go out in his car. I took a look and the caliper was stuck and wore the inside pad down to the backing plate and wore down the backing plate down so much it pushed the plate out of the caliper slides. I still don't know how he didn't notice the car pulling

 

It "appears" (photo can be distorted) the lower cam's have the shoes moved forward?

 

Probably don't need to buy new drums. They are expensive, and I'm not sure if they are made for 42-48 hubs. I do know they make them for 40-42 hubs, but it is rather involved to install because you will need new studs. And it's not just as simple as asking your NAPA man for some studs, because they aren't the same as the old Ford studs. Try to save those drums if possible. If they aren't grooved or warped, just clean the surface.

Show us a better picture of the hub, you might actually have 40-42 drums/hubs if the hub is inside the drum.

Also, when your buddy presses the pedal to check operation of the cylinders, don't let him press hard or fast. Might go out one side since the drum's not there to keep them even.

I think you could go 100 miles and those copper rivers won't ruin the drums. At the very least you should be able to try your other options before you add more symptoms.