Mismatched drums won't fit
 

I'm fitting hydraulic drums to my 30' model a . The fronts are sorted. I'm having trouble with the rear though. 3 of the drums look the same, the forth I didnt realize when purchased, doesn't look the same as the others and I'm having trouble fitting it over the shoes. I understand theres 2 drum styles from the era,but I thought you could use either. Any insight would be great.

Re: Mismatched drums won't fit
 

Those drums were obviously manufactured with the hub FLANGE inside the drum. That style drum was used on 1940 and '41 (some folks say '42 also) Fords, although they normally fit perfectly-well all the way up through 1948....absolutely a 'bolt-on' replacement. There were probably more than two iterations of those drums when you count NORS and replacement drum/hub assemblies. That one 'oddball' should go on, though.

Can you describe just where and when the drum stops 'going-on' the rear end? Does it stop when it meets the brake shoes. If so, it's possible the brake shoes are not adjusted to their most-retracted position. And if they are retracted all the way, and if you are working with new or re-lined brake shoes, many times now-a-days replacement brake linings are too thick, especially if you have drums that have never been, or minimally been turned. Is the key stock sitting properly in the keyway in the axle? Is there any way for you to accurately measure the inside diameter of that drum? It should measure somewhere between 12.000" and 12.060" in diameter. Could you take a picture or two of the brake assembly you're trying to install the drum over?

SOME replacement old Ford brake shoes have the big pivot hole at the bottom of each shoe punched in the wrong location and can cause your problem. Can you elaborate or shed a few more details? That black drum SHOULD work! DD

Re: Mismatched drums won't fit
 

Did you have the shoes arced to the diameter of the drums? That would result in the problem you are describing. The only problem you might have with the drums that have the hub on the outside is that they sometimes had welded on balance weights that would interfere with the wire wheels. Remember if you are running wire wheels on hydraulic brake drums you need a adapter ring. They just look like they are going to fit. See: https://www.fordbarn.com/forum/showt...=1#post1286293

Charlie Stephens

Re: Mismatched drums won't fit
 

WHY would ARCING the shoes to the diameter of the drums "result in the problem he is having"? And why confuse matters by talking about drums with "hub on the outside"? DD

Re: Mismatched drums won't fit
 

I dont have anything to measure something that large ,that precisely once . I tried to install the oddball drum and it didn't fit over the pads. I then grabbed the matching drum and it slid right over. I will check the adjuster and get a few more pictures.

Re: Mismatched drums won't fit
 

Check the size of the drum, if they are used and have not been turned they can have a ridge not letting the new shoes pass. Also the shoes could be oversized.

Make sure you have the adjusters turned inward to the lowest setting and if they are 39 /40 backing plates that the lower adjustment is turned to the dots facing each other.

Arcing the shoes is for proper fit to a turned drum. But it the linings are oversized and the ends of the linings are not chamfered they could be out enough to make the drum hard to install or not let it go on at all.

Also check were the shoes came from. Some of the brand new shoes are defective, try and use genuine ford shoes that are relined

Re: Mismatched drums won't fit
 

If the shoes are too thick they won’t go over the drums even when the adjusters are as far in as possible. Arcing solves this problem (plus allowing for full contact of the shoe on the drum).
He said in the initial post he is having trouble fitting the drum over the shoes.

I am talking about the drums with the hub on the outside because in his initial post he said showed a picture of the hub on the outside and said “I understand theres 2 drum styles from the era,but I thought you could use either. Any insight would be great.”

Re: Mismatched drums won't fit
 

"Arcing" does not NECESSARILY make a drum fit over shoes which have linings that are TOO thick. Arcing is meant to precisely fit the radius of a shoe's lining to the radius of it's drum, usually at the time of turning a drum to a larger diameter. If the shoe is not indexed properly in the arcing machine, or if set-up with the wrong dimensions, the drum STILL may not fit over the shoes. Arcing will not correct the situation of mis-located pivot holes in SOME aftermarket shoes, either. DD

Re: Mismatched drums won't fit
 

Although without the proper tools, you won't be able to accurately measure the inside diameter of the drums, you should be able to clamp two pieces of scrap side to side with the ends touching the inside of the "small" drum. Once you have them clamped, take them over to the "larger" drum and you'll be able to see what the difference is. I'm going through a similar situation but I'm using new drums and either new shoes or relined shoes. I don't know which. I have a 12" Starrett steel rule (slightly flexible) and it has to be flexed slightly to fit into both drums making me think that they might be a wee bit undersized.

Re: Mismatched drums won't fit
 

Depending on where you live Napa or O'Reilly etc should have a tool to measure your drums.

Re: Mismatched drums won't fit
 

I think I found my problem,or at least part of it. I've opted to install the rear drums upside down to allow clearance for the rear shock mounts,without having to cut up a good set of backing plates. Ive also installed the grease rings upside down,so the trough side is in the proper orientation . This caused interference with the brakes holding the shoes apart.Simple issue. The mismatched drum now fits,but still needs to be cut as it drags. I don't see any adjusters to bring the shoes in. Maybe I'm missing something?

Re: Mismatched drums won't fit
 

Interesting how more information comes out as these threads progress! :)

Glade you updated. So, are you saying the backing plates are on upside down? Not sure how the drum could be upside down. Not sure I'm understanding this quire yet, how does the wheel cylinder work inverted? Or am I totally confused on what you are doing.

Re: Mismatched drums won't fit
 

You have every right to be confused. When installing hydraulic brakes on an a' some will cut the real axle mounted shock ball as this ball will interfere with the wheel cylinder.Cutting this allows the backing plate
to be mounted as normal,but I intend to use that shock mount and so I I have mounted my backing plates upside down-so the wheel cylinder is at the bottom. Functionality should be the same. The issues will come when bleeding the system I'm sure.
Ever learning.

Re: Mismatched drums won't fit
 

He flipped his backing plates for shock mount clearance. Then he had to flip his grease cups for clearance for the slave cylinders.


And yes, I said that word. I don't buy into this new politically correct lingo.

Re: Mismatched drums won't fit
 

Alan is correct! At least a bazillion Model "A"s with hydraulic brakes are running-around with their rear backing plates mounted upside down, just because of that shock/spring mount interference. But simply turning the backing plates upside down is not the whole answer. You might want to read these two links below IN THEIR ENTIRETIES. Re-read if necessary to understand all of the implications. I like the method used in the first link. Your mileage may vary, though! DD

http://www.jalopyjournal.com/forum/s...d.php?t=124112

https://www.jalopyjournal.com/forum/.../#post-6849853

Re: Mismatched drums won't fit
 

When they are upside down it makes them hard to bleed the air out. It also repositions the shoes. Most of the old articles I've read over the years do it like this link.
https://www.lainefamily.com/ModelAFi...akeUpgrade.htm

It is a bit more work to weld up & redrill the holes plus cutting the notches but I think it's worth the effort. Les Andrews describes it this way in his manual. It solves the spring clearance problem and the rings for backing plate fit/alignment have been available from resto sources for a while now.

Re: Mismatched drums won't fit
 

Well, I learned something. I have heard of changing the clocking on the backing plates, but was not aware of inverting them. Very interesting.

Re: Mismatched drums won't fit
 

Educate me please: Do not the wheel cylinders have mismatched pistons??
Re clocking the backing plate has gone on in the A community for ages.
Paul in CT

Re: Mismatched drums won't fit
 

Ya, I don't understand the wheel cylinder thing myself. But, I haven't read the articles referenced.

Re: Mismatched drums won't fit
 

I've never done this, but did think about the inversion and how what we think of as normal would need to be done differently in this situation.

The cylinder needs to remain the right way up with the bleed nipple at the top, but be fitted at the bottom of the now upside down backplate.

I believe the circular register and the bolt holes on the back of the cylinder are not concentric with the bore so the holes in the backplate would need to be welded up and moved to put the centre line of the cylinder back where it should be.

The big end of the cylinder should point to the back. This would mean swapping cylinders left to right.
The long shoe should also be installed on the back.
Don't know about the grease retainer or the other problems associated with using hydraulics on an A but the things I listed above are what I believe to be right, but I've never seen them mentioned before (except by me).

Mart.