Technical BRAKES, Ultimate Guide To Fitting '39-'48 Hydraulic Brakes To Your 'A'....

This subject seems to come up alot on the HAMB, "How do I fit hydraulics to my Model 'A' ". Hopefully this should show how to fit said brakes the CORRECT way.

My Model 'A' came already fitted with hydraulic brakes, but the more I studied them the more things I noticed were wrong with the way they were fitted. The true horrors weren't discovered until they were actually removed from the car.

I decided the best way forward was to start again with a fresh set of backing plates.



Here is your basic '39-'48 Ford backing plate. In this case they are the later '46-'48 plate as they have the riveted rather than bolted bottom pivots. You will also need the correct hubs and drums as the original 'A' ones will not work with the hydraulic backing plates.

We'll start with the fitting of the front brakes first.
This is the stripped hub. You'll need a front fitting kit which consists of 2 bearing spacers and two backing plate spacer rings. You can see how these are mounted to the hub.
Take care with the backing plate spacers as they are cast iron piston rings and will break easily if forced.



The Model 'A' has a smaller backing plate stud spacing.
There is two ways you can approach this:

1. Elongate the original hole in the backing plate.

2. Plug the original holes and re-drill them for the Model 'A' stud pattern.

I choice the second as I believe this to be the correct way.



You can see in the above picture the now hole-less backing plate. A plug was cut from 3/8" steel rod and then plug welded both sides and ground smooth making sure not to remove material from the mounting surfaces.

Now is time to re-drill the mounting holes.
You can get complicated here and have it all set up on a rotatory table on a mill or do what I done and just mark it from the back!

The backing plate was masked with tape and placed on the hub.



With the backing plate mounted to the hub, making sure that the wheel cylinder is at the very top on the vertical, mark the position of the holes with a 3/8" drill bit, this will be your final hole size.



Use a drill press as this way you will have a nice straight hole. You should find that the backing plate sits flat making it easy to clamp down.



Use a small 1/8" pilot drill hole, double check everything and then keep enlarging the holes until you finish with a 3/8" hole.
If you find that its gone wrong somewhere, simple plug weld the hole and start again.



The finished article. Notice how close the holes are to the edge? Thats just the way it is I'm afraid.

If everything is correct it should all bolt up.



Complete the assembly of the brakes and its job done.



A little tip when assembling the brakes is to cover the shoes in masking tape. This stops the shoes getting covered in grease, oil and God knows what else.



That completes the front brakes and finally an example of how not to do it. Yes these are what were originally fitted to the car.

 

Moving onto the rear.

This becomes a little more involved and will need machineing to do it properly.

First off is the very outer edge will need 1/8" machined from it.





Also 1/8" will also need to be removed from the back of the rear drum.



The backing plate will sit on the rear axle casings and the holes will line up. You will notice that the backing plate will not sit flat because it will clash with the spring hanger.
The way to remedy this is a small clearance slot in the backing plate, as below.



For best results it will best have these machined on a mill as I had mine done. I would think a similar result could be achived with a angle grinder.

The following is the drawings to show where these slots will be in the backing plates. Remember that they will be handed.

Right rear.



Left rear.



With the slot the backing plate will now sit flat on the axle casing. Notice in the picture how the spring hanger now sits flush with the backing plate.



The second problem your now going to experience is that the wheel cylinders also have clearance problems with the spring hanger.
The way to overcome this is to rotate the backing plate forward. For reference the recommended number of degrees is 16. I found this not to be enough so I just rotated the backing plate until I had adaqate clearance with the wheel cylinder and more importantly enough space for the brake fitting and pipe.

With the backing plates held in position it was the same process as the front in marking the holes.
I used a 1/2" drill bit as this is the final hole size.





I removed the rear wishbones to make it easy to mark the holes.



Again the backing plates were drilled on drill press. You can plug the original holes but I chose not to.
Your final hole size 1/2".



With the rear backing plate mounted with a wheel cylinder you can see the amount of rotation. I kept the rotation to a minium to try and keep the wheel cylinder as high as possible.
If you look closely you can see how with the extra rotation of the backing plate how the clearance slot has moved round.



A shot from the back.



Before final assembly of the rear brakes you want to put a large chamfer on the outer edge of each brake shoe. This is because the shoe will rub on the inside of the brake drum.



Again some examples of how NOT to do it.
Apart from the obvious poor workmanship here the new mounting holes were actually drilled the wrong way so the backing plates rotated back not forwards. this had cause all sorts of problems with plumbing the brakes





Some final information.

When you tighten everything up you may find the drum binds. This may be due to wear on the tapers.
If this is the case you will need some axle shims. The car came with 2 but I found I needed just the one, the fewer the better in my opinion.



To finish you want to torque the nuts up to 80-90 foot pounds. this is important as its the taper NOT the key that holds the hub to the halfshaft. I find it best to put a wheel on the car and then torque the nut as this stops the drum from spinning.

 

Very nice. I'll be helping a friend do this soon. Great timing.

Mike

 

BTTT, great tech.

Cheers,

Drewfus

 

excellent

 

Bttt

 

Very cool...That answers a lot of my questions.

 

Excellent and thank you, printing this out for a freind..

 

This could not have come at a better time. I got a 29 coupe, in real great shape, back in April and got a complete set of 40 ford brakes including the spindles in June. I have been taking the brakes all apart, cleaning all the internal parts and blasting the brums & backing plates. All the parts were in really good shape. It looks like they had done a brake job on the 40, less than 5k miles prior, so even the shoes are in good shape. If i can ever make friends with my newfangled digital camera, will post some pics.

Thanks,

Mike

 

Don't take this the wrong way. It's a great post.

I am concerned about the lack of edge distance between the center of the hub and the mounting holes(which you already mentioned).

I know it is a limiting factor because of the diameter of the spindle, but the way you have your holes drilled is really not much stronger than the ones you showed as the bad example. I wonder if you could add a doubler on the inside to help displace some of the load? Like a circular ring?

 

Its a fair comment.

The backing I used actually has the reinforceing spacer ring you mention. They came from the factory like this and I believe they are from an F3 truck.

The difference between mine and the bad ones shown is that mine are securly located. The slots in the bad example are so inaccurate and sloppy that the backing plate had the oppunity to move on its mounting when fitted to the car.

Done properly with a single hole it doesn't matter where you apply a force on the backing plate it can not move.

I don't think there is a stength issue here.

 

Back again, this time, with a question or two. I printed this off and can't wait to get off work & get home.
What did you use for the master cyl portion of the system? Is it a single or dual type of master cyl? Where & how did you mount the MC? Is it directly operated off the brake pedal, asuming you kept the stock pedals? Or it it mounted via the original crossover bar, or whatever it's called, for the original mechanical brakes?

Thanks,

Mike

 

Good work.
Three comments/questions. (meant as constructive criticism, not nit-picking.)
1, The 80-90 lbs feet figure is surely too low.
I've read figures of 200-220 quoted, plus regular retightening and further tightening to the next castellation. (dont exceed 275 ft lbs) I think if anyone follows the 80-90 lbs ft figure they'll have trouble.
2, if you knew about the rotation before cutting the clearance slot in the rears, would you have made the cut out slightly different.?
3, Do you think they'll bleed ok with that much rotation? I'm not saying they wont, I just wondered if this is an established method, and people have tried it before and it's ok.
Nice documentation and presentation, glad to see you're doing the car right.
Mart.

 

Just thought of something else.
Is it not an established technique to use the rear backplates upside down? This just rings a bell from somewhere, I've not tried it myself. That would keep the cylinder and the backplate ridge clear of the spring mount. Anyone else seen it done this way?
You'd have to fit the cylinders the right way up of course so they would bleed ok.
Keep up the good work.
Mart.

 

very good.....nice work.....quality.....

seems like you posted pics of those poorly done backing plates before....

 

i have a fixture to offset drill the holes for the rear
i will loan it out to any hambers
as long as i get it back
3 sets of holes
original bolt pattern with dowel pins for location
offset 15deg forward
offset 15deg backwards
let me know (p.m. me)
but i will sick the hamb mafia on you if its not returned
tom

 

No problem, if there something wrong I would rather know than cause problems to myself or someone else.

I've checked three different publications and now have three different torque settings!
The first is the 80-90 ft lbs the second is a larger 125 ft lbs and the third says tighten well!
I'll look into it further.

Of course if I'd known about the position of the slot I would have done it differently.

They have already been bled and are fine. Even though the backing plates have been rotated the wheel cylinders are still the highest point.

Yes, you can mount the backing plates up-side down.
I personnely don't like this way as it puts the wheel cylinder very low, which may cause problems with bleeding the system. Also the brake line will run very low leaving it vunerable to being damaged.

 

Fair enuff, Clark.
I got the torque info from the flatheaders techno site, here's a link:
http://groups.msn.com/FordFlathead1932to1953/technositelink.msnw

Cheers.
Mart.

 

I've got a feeling my A manual mentions 100lb for the rear hub nut. Haven't got it to hand right now, but I'm pretty sure it is and mine has been set up with that figure.

Regarding the backplates, I remember that Simon Watts positioned his rear with the cylinders at the bottom on his RPU. Not sure whether he had any problems with bleeding them.

Another question, Clark. Are your rear radius arms mounted the correct way round or have they been swapped over?

 

Not sure what you mean?

 

Bitchen!

I'm gonna do this to my model A too!

No more "Lovin' the feel of steel from Pedal to Wheel!"

Sam.

 

See my post. Weld in the spacer between the backing plate and spindle
http://www.jalopyjournal.com/forum/showthread.php?t=124317

 

The master cylinder is attached to the new battery box which you made just for that purpose. New cylinder $30, box--free if you make it and the linkage

http://www.mtcarproducts.com/batbox.htm

 

There is another solution for the rear brakes.
You dont have to remove any from the outer edge of the backing plates,
you dont have to remove any of the outer edge of the drum,
you dont have to grind away any of the shoes.
You dont have to rotate the backing plate to funny angles.
Take out the lug studs.
Separate the hub and drum
Position the backing plate so the wheel cylinder clears the spring hanger and is in the upright position.
Mount the hub properly.
Calculate the distance the drum needs to be moved out to fit properly.
Make a spacer to fill that space.
Install new longer studs
As a bonus, you can change brake shoes in the future without pulling the hub.

 

When my quick-change was delivered, the instruction sheet spoke about having to mount the radius arms on the opposite side and upside down. The is because the torque tube input is lower on the quickie than on the original banjo centre section and the arms won't line up. If you flip them over, they do. Dead easy.
When it actually came to fitting the built-up axle to my car, because my car is standard height, the spring wouldn't line-up to the hangers on the axle ends because of the extra angle of the t-tube. To counter this, the ends were taken off and new mounting holes were drilled in them to compensate for the angle, thus 'straightening' the hangers. After doing this, the radius arms then went back on to the axle in their stock position.
I was just wondering how whoever had built your axle had got around that.
I spoke to the guy who manufactures these quickies on the 'phone and he confirmed that the arms normally need to be swapped over, and I know that Neil has already had his axle ends drilled to counter the extra angle on the hangers incurred by the quickie.
PM me if you're unsure about what I'm on about.

 

Oh right, I see where your coming from now. I never ever got the original instruction sheet for the quickchange so I'm a bit clueless to how it goes together.
Couldn't send me a copy of yours could you?

 

A very good post regarding the 40-48 front brake swap for Model A's...I love these cars, and have 7 in my collection...

But there's a few things I learned over the past 34 years. My two cents worth regarding the rear brake backing plates. I didn't like the idea of making the "window" cuts in the backing plates.

I removed the wheel cylinders and to take care of the interferance with the spring mount perch, I heated the area red hot with the torch and forged a dimple so I wouldn't have to cut the two windows. This way there's less open to the weather and dirt.

Another thing I did. I did this adaption in 2001 when I had the rear end torn down for some work. I had a machinist friend with a big lathe cut 3/16" off the face of the mounting flange on the rear end housing for the backing plates. That cost me $20. This pulled the backing plates in so I wouldn't have to use shims to space out the hub. In your case you trimmed the brake drums. Either case it involves some machining to effect the same result.

I found thru the years that using the shims didn't work well for me, as they wore out every year, and I was always replacing them and the keys. Luckily I kept ahead of this on a yearly basis and didn't screw up my hubs or axles.

I gleaned this info from California Bill's book on the Model A....I found a reprint of this 1952 book in a bookstore for $5!.

This saved me the yearly inspections and replacement of shims and keys.

Nice article.

 

Curious about the combination battery box/master cylinder mount.

got any pictures of that?..

Thanks, Mark

 

For the benefit of Michael_e and abonecoupe31 here is some pics of my master cylinder and adaptor.

I originally had the MT products combination battery box and master cylinder (Linked further back.), but to be be honest I found it....well....horrible.
Nothing wrong with its construction or action it was just not for me, basic, bulky, poorly designed and very "agricultural".

I dumped all that and bought a Clings, which wasn't cheap but the quality, fit and design are just out of this world.

www.clingsaftermarket.com

There is two diiferent kits, one for an 'A' box and the other for the V8 box. Basically the same but you have a pedal adaptor built in with the V8 version.