Factory Brake Job

[TodFitch]

My theory is that when pressure is applied to a brake shoe that is out of adjustment it causes the leading edge to rotate about a single eccentric axis. This can result in an acute angle forming  between the toe of the shoe and the drum, causing the wheel to lock-up. Because of the design difference (1-wheel cylinder front vs 2 rear wheel cylinders back) This condition can only happen to the front brakes...maybe..

Not sure what you are trying to describe, but the "leading shoe" will be self-energizing (i.e. once the shoe contacts the drum the rotation of the drum will tend to pull the shoe out a little more). Basically a simple form of power assist. And a dual wheel cylinder setup is to make both shoes leading shoes.

 

I believe the Bendix drum brake setup allowed both shoes to move with the drum for the same self-energizing effect and for years Chrysler dissed that as being too grabby and thus the smooth controllable action of the Lockheed setup was better. Didn't hear much about that argument after Chrysler adopted Bendix in the early 60s though.

 

Very difficult to make disc brakes self-energizing but I did hear of some early systems where the calipers could rotate slightly and had some sort of wedging mechanism.

[HanksB3B]

Obviously the very best situation is to have new drums and shoes and the Ammco 1750 or the Miller Tools MT-34-B.

 

I forgot to thank you Tod a few posts back. # x & #23. As a final touch I think sandpaper adhered to the drum and turned during the adjustment stage would be beneficial in obtaining the largest contact patch achievable without the benefit of a brake shoe sander.

 

Can't wait to get down to the truck,

 

Hank 

[Jeff Balazs]

Accurately might not be the correct word but the blacksmith in me got the better of me today I guess but here goes:

 

Working on this truck has become a vice.

If you bisect and angle each leg is equal in length.  

Bisect again and it starts to become an arch.

To be continued...

 

Hank 

 

Things seem to be coming together. Anticipating a successful test ride tomorrow.

Hank;

Your eyes must be a heck of a lot better than mine. I am sure you will get it close. You might be able to find an old school brake shop that would do this for you if you bring them in? I know there is a shop in Long Beach that does amazing things to drum brakes for vintage racers. You could really impress 48Dodger with a set of drilled and race tuned drums. From what I understand they would probably as good as disc's.

 

I have made a lot of parts with a vice, a hacksaw, the drill press and files. So I do appreciate what can be done if determination is applied. It may take a few attempts to get things just so........but then you can say I did it myself. And that is a good feeling.

A few weeks back my son-in-laws Grandfather was here for a visit. He retired as the head of R & D for Boeing and has been around machinery his entire life. He could not get over how quiet my truck was. My favorite comment of his was " I was around when these trucks were new.....I remember them clearly and they were never that quiet". He kept wanting to know what all I had done to get it this way. Made me feel pretty good about going the extra mile on some of these details.

 

Jeff

[HanksB3B]

Guys,

 

I could use some help. The problem that prompted getting back into my brakes was that the left wheel was grabbing. Today there was no way I could get brake pedal pressure even after bleeding all six slave cylinders. Is it possible that my brake problems are a "perfect storm" and that what I thought was just a malfunctioning brake shoe has somehow become a rebuild/replace the master cylinder. Is there something I'm not understanding ? 

 

Thanks in advance,

 

Hank 

[Jeff Balazs]

Hank;

You might try backing off the pedal adjuster. It is just possible that the pedal adjustment is preventing the rod from fully retracting. I ran into this condition when setting up my new Cherokee M/C.

 

hth   Jeff

[HanksB3B]

Good morning Jeff and thank you. I delayed removing the MC in hopes of hearing something like that. Wish me luck. How is the commissioning of your truck going. There's at least two forum members in LA County waiting to get a look.

 

Hank

[HanksB3B]

I went through my little inventory bucket of brake cylinders and MC's (see attached). I ordered a rebuild kit from NAPA and a new Raybestos MC from VPW. 

 

I could use some advice:  

 

The silver one (the only part that was ever the right color) was on my truck when I bought it. It does not look like the one now intlalled in my truck that I bought from Gary Roberts two or three years ago. (shown below) 

 

 

• Even thought the silver one functioned for years, I was told it was really for a passenger car. Is that correct ?
• The red slave cylinders were replaced with new from Roberts at the same time as the MC.
• The four other rust colored slave cylinders were removed from all four wheels of (my best guess) a 1950 3/4 ton. (but I think they are the same size as the two I use up front)

I need a bit of machinists advice:

• What could/should be done with these parts ?

Answer to my own question:

1. Give away the MC's for the passenger cars. 
2. Soak and dissasemble the truck slave cylinders.
3. Measure the tolerance and determine if they can be honed and rebuit..

 

Thanks in advance,

 

Hank 

Edited February 27, 2014 by HanksB3B

[Jeff Balazs]

Hank;

So? No luck backing off the pedal adjustment? I am pulling for you. This was probably too easy to have worked,

 

I am just about done with my truck. Couple of relatively small things now. Been super busy so time has been at a premium.......but have been getting things checked off the list.

 

Jeff

[Dave72dt]

With solid flow of fluid from each bleeder and no pedal pressure, you're only left with a couple of things that can cause it that I can think of.  The check valve in the master cylinder or shoe adjustment.  I'd suggest locking up all the shoes by shoe adjustment, rebleed them and check for pedal pressure.   That should give you the same effect as plugging a line without opening it to air. Too much clearance could be using up all the fluid  your master can pump out.  Then you can go back to release the brakes from lockup, one wheel at a time.

[HanksB3B]

Hank;

So? No luck backing off the pedal adjustment? I am pulling for you. This was probably too easy to have worked,

 

I am just about done with my truck. Couple of relatively small things now. Been super busy so time has been at a premium.......but have been getting things checked off the list.

 

Jeff

 

 

With solid flow of fluid from each bleeder and no pedal pressure, you're only left with a couple of things that can cause it that I can think of.  The check valve in the master cylinder or shoe adjustment.  I'd suggest locking up all the shoes by shoe adjustment, rebleed them and check for pedal pressure.   That should give you the same effect as plugging a line without opening it to air. Too much clearance could be using up all the fluid  your master can pump out.  Then you can go back to release the brakes from lockup, one wheel at a time.

 

Thank you both so much for responding,

 

Jeff no I have not yet tried backing off on the pedal adjustment. There is no real reason I can think of that the master cylinder with less than 500 miles of service should be acting up. I guess it's possible that brake wear caused a perfect storm with a piston that was just a bit too long (but functioning) from the initial rebuild of my brake system performed by me. I now have a rebuild kit from NAPA but before I rebuild it I will reinstall it and get used to adjusting the rod. A master cylinder is one of the things I did not have in reserve.

 

Here's something: A very, very experienced old guy with very old cars keeps his cars in top shape by removing a perfectly functioning component part (like a waterpump for example) and puts it away. This way he knows the part was functioning perfectly before it was stored and not a part that could fail from new un-tested over the parts counter.   

 

. These past 3 or four days of rain and sun have been awesome.

 

If I could fill a 5 gal bucket from the storm two nights ago and triple that last night...on just my little truck..makes me think how much volume in gallons clouds can hold. Looks like more on the way Tim.

 

And now for a confession: I have not (although its now scanned) and in duplicate glove box copy, I have not studied the brake section carefully enough.

 

I'm hoping it's what Jeff thinks, but glad a new master cylinder is on its way from VPW. 

 

Dave, Thanks for that tip, it's a good one.  I have a "one-man bleed your brakes" pump but couldn't get it to work. I also have a modern car nylon power/flush pump (like a garden bug spray unit) which would allow me the ability to feed the master cylinder under pressure continuously,   PROVIDED THAT I can make ? find ? a fill cap for the master cylinder  Any ideas anyone ? 

 

In the mean time I guess I'll work between rain storms on the fabulous Gauge kit I got from Keven. Beats scrapbooking on a rainy day hands down! Might be the best $125.00 you could spend.  

 

 

(but since this is a thread about "Factory Brake Setup", may I ask please don't post about anything else if I go off topic. (don't want to mess up the thread).  

 

Hank 

Edited February 28, 2014 by HanksB3B

[Merle Coggins]

. These past 3 or four days of rain and sun have been awesome.

 

 

Hank 

 

LOL!! That brings back memories Hank. That is one of the reasons I added a tonneau cover on my truck. I was tired of draining the pool in the bed every time it rained. I kept a short piece of hose handy and used it to siphon out the water every time. Now the tonneau helps support the truck cover and I don't get a pool every time anymore.   

[Jeff Balazs]

Hank;

I don't know for a fact if the stock master cylinder can behave in this way.......but on some M/C's if the piston does not fully return then you can pump and pump and never make the fluid flow. It has to do with the position of the seals in relation to the inlet orifice. I don't have a stock M/C to check so I really don't know if this is the case with one of these. It seems to me if your M/C was functioning properly before you started this project then there is a good chance it still is. Especially one with low wear on it.

 

I do know that if the pedal adjustment is not correct it can easily prevent the piston from making it all the way back. I have run into this condition with my Cherokee M/C modification and it causes the system to retain a bit of pressure and make the brakes drag.

 

It is worth checking......might just solve the situation.......and it only takes a few minutes to readjust. All you will need is a 5/8" and a 7/8" open end wrench and a light.

 

As far as bleeding the system you should not need any special equipment. A lot of folks like these "new fangled" auto fillers but I have never found them necessary. Just one more thing to break or malfunction. Simply find a helper.....they do not need to possess any particular skills.... except to have a right leg and follow your directions. If the components in your system are all functional and leak free ...... bleeding it shouldn't take more than about 10 or 15 minutes from start to finish. I like to start at the wheel cylinder farthest away from the M/C......but on a simple system like these trucks either direction should work. Go all the way around (from bleeder to bleeder) 2 or 3 times and all should be good.

 

Hope this helps. Jeff

[HanksB3B]

Hank;

I don't know for a fact if the stock master cylinder can behave in this way.......but on some M/C's if the piston does not fully return then you can pump and pump and never make the fluid flow. It has to do with the position of the seals in relation to the inlet orifice. I don't have a stock M/C to check so I really don't know if this is the case with one of these. It seems to me if your M/C was functioning properly before you started this project then there is a good chance it still is. Especially one with low wear on it.

 

I do know that if the pedal adjustment is not correct it can easily prevent the piston from making it all the way back. I have run into this condition with my Cherokee M/C modification and it causes the system to retain a bit of pressure and make the brakes drag.

 

It is worth checking......might just solve the situation.......and it only takes a few minutes to readjust. All you will need is a 5/8" and a 7/8" open end wrench and a light.

 

As far as bleeding the system you should not need any special equipment. A lot of folks like these "new fangled" auto fillers but I have never found them necessary. Just one more thing to break or malfunction. Simply find a helper.....they do not need to possess any particular skills.... except to have a right leg and follow your directions. If the components in your system are all functional and leak free ...... bleeding it shouldn't take more than about 10 or 15 minutes from start to finish. I like to start at the wheel cylinder farthest away from the M/C......but on a simple system like these trucks either direction should work. Go all the way around (from bleeder to bleeder) 2 or 3 times and all should be good.

 

Hope this helps. Jeff

 

Thanks Jeff. I plan on painting (something I failed to do) the current master cylinder, install it and then if after following the Truck Manual's instructions adjustment the pedal adjuster. If I can't make it work the new VPW master cylinder will be installed and the current one rebuilt for back-up.

 

Hank 

[deathbound]

Hank;

Your eyes must be a heck of a lot better than mine. I am sure you will get it close. You might be able to find an old school brake shop that would do this for you if you bring them in? I know there is a shop in Long Beach that does amazing things to drum brakes for vintage racers. You could really impress 48Dodger with a set of drilled and race tuned drums. From what I understand they would probably as good as disc's.

 

I have made a lot of parts with a vice, a hacksaw, the drill press and files. So I do appreciate what can be done if determination is applied. It may take a few attempts to get things just so........but then you can say I did it myself. And that is a good feeling.

A few weeks back my son-in-laws Grandfather was here for a visit. He retired as the head of R & D for Boeing and has been around machinery his entire life. He could not get over how quiet my truck was. My favorite comment of his was " I was around when these trucks were new.....I remember them clearly and they were never that quiet". He kept wanting to know what all I had done to get it this way. Made me feel pretty good about going the extra mile on some of these details.

 

Jeff

 

I think Jeff is referring to CH Topping (http://www.chtopping.com/), near PCH & Magnolia. I've used them a few times, great service. They can arc your shoes (or supply new ones) to your drums, which should be turned for a true surface. I'm in Long Beach & have an Ammco 1750 if you want to borrow it. Derek

[Jeff Balazs]

I think Jeff is referring to CH Topping (http://www.chtopping.com/), near PCH & Magnolia. I've used them a few times, great service. They can arc your shoes (or supply new ones) to your drums, which should be turned for a true surface. I'm in Long Beach & have an Ammco 1750 if you want to borrow it. Derek

Exactly. Couldn't remember the name.... but that is the place. These guy's do some really amazing stuff with drum brakes.

 

Hank; There is no need to paint a M/C. I doubt if you could get the paint to last all that long on one anyway. Besides all the important stuff is on the inside.

 

Jeff

[HanksB3B]

Hank; There is no need to paint a M/C. I doubt if you could get the paint to last all that long on one anyway. Besides all the important stuff is on the inside.

Jeff

 

Hank;

You might try backing off the pedal adjuster. It is just possible that the pedal adjustment is preventing the rod from fully retracting. I ran into this condition when setting up my new Cherokee M/C.

Jeff

 

 

Hello,

 

Does anyone know what the correct factory dimension of the master cylinder pushrod (see figure 9)

 

 

Here's a couple of my old master cylinders. I think they are either an earlier sieres of trucks like the W series or possibly from passenger cars? The Silver one was actually on my truck  when I purchased it and worked for many years. The one one the bottom was acquired somewhere along the way. The silver one is far easier to clean up and put back into service than the deeply rusted unpainted one is. The reason I like my master cylinder painted is that rust is dirty and when it comes to handling the body during the rebuild process everything should be as clean as possible. I know that brake fluid dissolves paint. but I'm real careful topping off.

 

 

 

The three combined pictures above are progress pictures of my current master cylinder.

 

I almost couldn't believe my eyes when I was reading this. Jeff mentioned this in post #___:

One thing I could do is to scale this drawing to full scale and use it to approximate the distance at "B" and "C' of the illustration above.

 

 

If you look closely at the picture above, forensics (the 1/4" length of rusty threads) indicate that the master cylinder push rod has been moved. I'm pretty sure this is what is causing my brake lock-up. 

 

 

My plan is to move the lock nut and adjusting nut back as far as the rusted threads indicate they were, clean up (and paint) the pushrod and without rebuilding my master cylinder reinstall is and take the truck for a test drive after the brakes a bled. Is there a worn and right way ? Do the brake farthest away ? What is the best practice ?

 

Thanks and stay tuned,

 

Hank 

Edited March 5, 2014 by HanksB3B

[Young Ed]

Hank  yes having that rod too long will cause your brakes to lock up. You need to adjust it to have the proper amount of freeplay. The shop manual should have a procedure or at least a spec for the amount of freeplay. I'm thinking 1 inch.

[ggdad1951]

I'm thinking you hit on the problem Hank.  When I put my MC back together after re-plating the push rod I reset to a calipered measurement and had no problems.

[Dave72dt]

If you taker a good look at the cutaway, you'll see the pushrod is not attached to the piston.  As long as you have free play and the piston comes all the way back and is correct for that master, Port C is uncovered.  The lock ring that holds the parts inside is the piston return stop.  The key is ensuring the piston fully retracts smoothly  and easily and the free play is correct.  The nut movement .is done to adjust the free play and to match it to the individual differences in trucks in linkage wear points and cab movement  that may have changed pedal return height.  It rarely needs to be readjusted.  What y9ou may have done when bleeding is move the piston further  in the master than in normal braking and it's not  returning the way it should.

[HanksB3B]

Thanks Guys,

 

I'm thinking when I re-mount the MC I should be able to set it freely against the support member that it bolts up to without the push rod exerting any force or interface with the piston. Then I should insure that the one inch of free play is really there when I adjust the lenght of the push rod. Mark when you said "calipered measurement" precisely what do you mean ?

 

Maybe I'll be driving today ?

 

Hank   

Edited March 5, 2014 by HanksB3B

[TodFitch]

At least on my car, which uses an older version of the master cylinder in your photos, setting the free play is quite easy. If you move the brake pedal by hand you can actually feel when the push rod comes into contact with the piston. And you can do it from under the hood, so it is simply a matter adjusting the nut then feeling the result. When close enough for your satisfaction tighten the lock nut.

 

On the late '30s and 40's cars with the master under the floor I don't know if my method is possible, but I'm guessing it is on the trucks as the master cylinder for them bolts right onto my car (I used one until I had my original one re-sleeved).

[Merle Coggins]

Yes, like Tod says... from under the truck, where you can access the adjustment, take the return spring off the pedal so you're not fighting that resistance. Then move the pedal by hand to feel how much free play there is. You should be able to move the pedal slightly from it's "At Rest" position to where contact is made between the push rod and the M/C piston. The 1" rule is measured at the foot pad at the top of the pedal. You could confirm it from there before reinstalling the spring. You can do this with the spring connected, but it's easier to feel without it.

 

Merle

[HanksB3B]

Thanks everyone for the good info, 

 

 I'll print the comments above and be under my truck isoon. 

 

I really appreciate all the help, 

 

Hank 

[ggdad1951]

Thanks Guys,

 

I'm thinking when I re-mount the MC I should be able to set it freely against the support member that it bolts up to without the push rod exerting any force or interface with the piston. Then I should insure that the one inch of free play is really there when I adjust the lenght of the push rod. Mark when you said "calipered measurement" precisely what do you mean ?

 

Maybe I'll be driving today ?

 

Hank   

Hank, I measured w/ a caliper where the nut should be so I could put it back where it belonged since i took it all apart for re-CAD plating.  I might have the measurement at home someplace.  

[Dave72dt]

Hank, I measured w/ a caliper where the nut should be so I could put it back where it belonged since i took it all apart for re-CAD plating.  I might have the measurement at home someplace.  

That distance can vary depending on how his cab sits on the frame in relationship to the master cylinder mount, how far back the pedal comes against the floor and how much play is in the pivot bushings, pins, etc.  All of those things may not be exactly like yours so the distance can be different and be correct.  As long as he has the correct free play adjustment, it doesn't matter where the nut gets locked down at.

 

 

If you want to experiment, shorten the rod on your truck about 2 full turns and see what it does to the free play, measuring before and after.

Edited March 5, 2014 by Dave72dt