1 1/2 ton/COE/ big truck owners...

[Ron in AZ]

....... I need brake help.
I have a 1947 COE , it has the stock front brakes that I rebuilt the wheel cylinders and turned the drums, the shoes were in very good shape and matched the curve of the drums .
The rear end is from a mid 70's motorhome (same bolt pattern to keep the look ) that I also went through and turned the drums , the shoes were like new when I got it and the wheel cylinders were in as new shape also.
I installed a 1 1/8" dual bowl master with a dual pancake booster....
It has a good peddle but....... it dose not stop very good at all.
I can not lock the wheels at all and when I stomp on the peddle to stop at a light I can push the peddle to with in an inch or two of the floor.
Would a residual valve help ?
I think I have the drums ajusted as close as possable before drag becomes a problem.
I have been working on this truck for months getting it ready to hit the road and want to start driving it around but it's too unsafe to do so.
A lot of hard work done but can't enjoy it yet !!!
HELP.... Ron in AZ

[Kurt in NJ]

If you turned the drums, then reused the shoes that were worn to the old drum diameter you no longer have good shoe to drum contact

why all the changes? --Having run a 46 truck for many years with about a 2 ton load the stock 2 speed rear worked well, the truck got 15 mpg with the load, and stopped as good as a more modern truck with the same load

If you have driven this truck a ways you can take the drums off and the contact areas should show,should be over 75%, perhaps your master cyl mounting is flexing, and perhaps you still have some air in the system

[Ron in AZ]

Kurk, thank you for the reply,
This truck sat for about 25 yers or more before I bought it and got it running.
I changed the rear because it had a 6.66 single speed R&P and did not go over 30 mph.
The drums were rusty (front)and all wheel cylinders were stuck .
I only had a light cut taken to get rid of the rust on the front drums .
I am about to remove a drum to check things and will check the contac surface again.
No flex in the master mount either.
Thx

[47COE]

My truck's brakes are all stock without a booster, so I can't be much help with your setup. But in nearly 40 years of driving it I can't remember ever locking up the wheels to cause a skid.

Without trying it myself, I can't say whether there is a problem with your brakes, or with your expectations.

But when you do get it on the road you'll have a lot of fun with it.


Tom

[scrapiron]

Did you have instructions to properly bleed the booster?

[Ron in AZ]

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It is a vaccume booster and I added a small resurve can so I don't run out of vaccume.

Also, living in Tucson you never know when you need to lock up the brakes I drive a safe distance away but somebody is always in a hurry and may pull out in front of you....
The crazy western drivers....!

Thx ..

[Dec211975]

I can't think of a drum brakes system that doesn’t have a residual valve of about 10 psi or a combination valve ( proportioning valve), with out that residual pressure I could envision air being sucked back in to the hydraulic brake lines because there would be no pressure to keep the lips in contact with the wheel cylinder’s wall.

[Ron in AZ]

Dec211975,
I think you hit it on the head !
After I drive the truck I see that there is brake fluid dripping off the master cylinder and could not understand it.
It must be doing just as you said, sucking air back and then making pressure in the master and pushing out air/fluid in the bowls...!!!
That is what I am going to try, would you use one for each system front and rear or only one for the front?
It has a dual bowl master so it has separate lines one front one rear.
Thank you for the input !!!

[Dec211975]

You should use one on both the front and back 10 psi. A proportioning valve (Combination valve) would be a better solution if you can find one. If I remember correctly the front brakes should be applied first gently, and then the rears apply with more pressure, which is why a combination valve would be preferred, it would contain both of the residual valves as well as the proportioning valve. Speedway has a non-adjustable proportioning valve that I think has the residual valves in it. With your truck you may want an adjustable proportioning valve as the brake performance will change with the amount of weight over the rear axle. (Sorry I am just thinking out loud). It would probably be wise to call a supplier and see what components they recommend. Good luck with your project.

Regards,

Brian

[sturgis 39]

Originally Posted by Dec211975

I can't think of a drum brakes system that doesn’t have a residual valve of about 10 psi or a combination valve ( proportioning valve), with out that residual pressure I could envision air being sucked back in to the hydraulic brake lines because there would be no pressure to keep the lips in contact with the wheel cylinder’s wall.

I might be wrong but residual valves are for disc brakes.

I would go back to the original rear end and install an over drive transmission. Dual master cylinder may be the problem. The front brakes may require less travel than the rear brakes or rear brakes might require less travel. The pedal travel may be stopped because the front brakes are applied before the rear brakes.

[sturgis 39]

Originally Posted by Dec211975

You should use one on both the front and back 10 psi. A proportioning valve (Combination valve) would be a better solution if you can find one. If I remember correctly the front brakes should be applied first gently, and then the rears apply with more pressure, which is why a combination valve would be preferred, it would contain both of the residual valves as well as the proportioning valve. Speedway has a non-adjustable proportioning valve that I think has the residual valves in it. With your truck you may want an adjustable proportioning valve as the brake performance will change with the amount of weight over the rear axle. (Sorry I am just thinking out loud). It would probably be wise to call a supplier and see what components they recommend. Good luck with your project.

Regards,

Brian

Proportioning valves are usually used on drum disc brake combinations. Disc brakes on the front and drum brakes on the back. Dual master cylinders are not as great as some people think. They do not give you two separate brake systems. They are interconnected in the master cylinder. When the front or rear system fails, there will be additional pedal travel to apply the functioning brake system.

I am sure there will be response from some brake experts. Proportioning valves, residual valves, a dual pancake booster and dual master seems like a combination that may create more problems and a non functioning brake system

[sturgis 39]

I question proportioning valves on a dual master cylinder system. I question residual valve on a drum brake system. I question the out put of the dual master cylinder-is the output from both systems the same. Maybe the dual master cylinder you are using is for a combination of disc brakes and drum brakes.

The early Ford v/8 garage is an expert on brake systems for old Ford. I never remember his name. Maybe he will respond. Vern Lacy is his name.

[Bob C]

Disc brakes do not use residual pressure valves.

Bob

[sturgis 39]

Originally Posted by Bob C

Disc brakes do not use residual pressure valves.

Bob

I think you are wrong. There is no adjustment on disc brakes as compared to drum brakes. The pads wear on disc brakes and you can not adjust the pads so they are closer to the disc. The residual valves keep the pads close to the disc as they wear down. I could be wrong but I do not think there are residual valves in brake drum systems. Maybe, they will address this issue on the View or Doctor Phil.

I just looked at a couple of web sites. I did a search for residual valves. They conflict with each other about residual valves. One site says they are used on disc brakes only and another one says they are used on drum and disc brakes. The residual valves are built into the master cylinder on some cars according to another site. The only thing that was common on the websites was that residual valves are used to prevent excessive pedal travel.

I am no expert on brake systems and I have not been certified by a sanctioning organization.

[FlatheadTed]

Residual valves are used to give bi-yest due disks on the front being more efficient ,most modern cars require them set up according to weight distribution .If the displacement of your master is less than the wheel cylinders you will get pedal travel .If you can get us a photo of your backing plate we may be able to give some advice on linings etc .Its important to have the correct material .

[Chris Nelson]

If your master cylinder has no residual valve built into it, and some do have them, you need one for the front and for the back since you are using a dual master cylinder. Check with the manufacturer to see if it has the residual valve built in. If memory serves me right, when I built my two cars, the brake manufacturers recommended 10 lb residual for the drum brakes and 3 lb residual for the disc. Modern cars use a proportioning valve to do the same job.

[sturgis 39]

Originally Posted by Chris Nelson

If your master cylinder has no residual valve built into it, and some do have them, you need one for the front and for the back since you are using a dual master cylinder. Check with the manufacturer to see if it has the residual valve built in. If memory serves me right, when I built my two cars, the brake manufacturers recommended 10 lb residual for the drum brakes and 3 lb residual for the disc. Modern cars use a proportioning valve to do the same job.

I think you are wrong. Maybe Mr. Flat Head Ted or Mr. Lacy from Early V/8 garage will correct this statement being made by me if it is not correct. The proportioning valve and the residual valve do not perform the same function. The residual valve keeps pressure in the line to keep the brakes from backing away from the contact surface. I guess the contact surface can be brake drums or rotors. The portioning valve is for applying the front brakes or rear brakes harder. I think the front brakes do most of the braking in modern cars. The two valves are called by two different names because they have two different functions. They may manufacture a combination valve that does both functions.

I am not a certified brake expert with 200 years of experience in some brake shop. I am not a brake expert and do not plan to be a brake expert.

[Ron in AZ]

First I am going to check a few things , but the master has no built in valve.
I just bought a 10 lb one today.
I'll be removing the drums to see how much of the shoe is contacting the drum and go to the valve install after getting the shoe surface to drum correct .
Before the last time I drove it I had switched the front and rear lines on the master and it seemed to help.
It will be the weekend before I get to work on it again.
Thanks to all of you for the help and suggestions, some how I am sure it will get fixed.....
Its just that the weekends don't come around fast enough !... (and I work for my self ) My boss don't let me off during the week .
Thx .....Ron in AZ

[Dec211975]

Disc brakes usally require no residual valve due to the nature of the square cut seal that pulls the caliper piston back into the Bore. I will admit I don't know as much as a lot of you on the Ford Barn on early Fords but after 25 years as an ASE certified Master Tech I have a pretty good understanding of Brake systems. Its not my first Rodeo.

[sturgis 39]

Ron

Will you be posting some pictures as requested by Flat Head Ted?

I love those COE and I have one but It is kind of rough. There are actually bird nests in the headlight buckets. They look tall but you can still talk to the driver without standing on a ladder. GM and dodges were really tall and I think they called the GM a two story.

Post cutters use to use them around here in the fifties. The post market has been kind of in the dumps the last 20 years and the forest service does not wright little contracts that were called "Ranger Sales". The post cutters use to get about $120 a load delivered to the sawmill. There were a lot of expenses that ate up the $120. They could get a load a day and get to the mill before 6PM but they usually started at 5AM.

You would see all kinds of one and half ton trucks coming down the highways with smoking brakes and smoking engines. Most of the post cutters loaded by hand and they were tough. Green trees are heavy because of the moisture content.