Cast-iron brake drum fit

R

Richard Lorenz

Senior Member
I have a set of new cast-iron brake drums that are too tight to go on with shoes that have new woven linings. Is this the usual case?

Also, do the new drums need turning in order to be centered properly?
 
Hi Richard, been a long time since I have seen one of your posts.


In a nutshell, yes the drums need to be machined to ensure they are centered onto the hub. At that time, the linings are generally arced to the (new) size of the drum. With both of those done, the drums usually slide right on. The only time we see grief is from the e-brake band linings sometimes being too thick.
 
I recommend that the drums be turned after they are installed on the hubs to make sure they are true.


Some of the new drums are slightly undersize so they can be finished turned to 11.000 inches as the original factory drums were.


Also the shoes should be arced to fit the finish diameter of the drums.


This is what I have done for many years with very good success.


Chris W.
 
Yes you need to have the shoes arced and maybe a slight cut to true up the drums if this was not done. Have you inquired where you purchased the drums/shoes if they could do the work? Put your general location in your profile and someone might suggest a place to have this done.

Charlie Stephens
 
I had to have the Plasmeter drums that I used in the mid 90s turned about thirty thousants to get them on. Grinding or filing s taper on both ends of the lining also is a big help . I taper the ends of the lining all the way up to the end rivets . The ends of the lining usually kicks out a bit after riveting , that is why I taper the ends of the lining . If the shoes are not properly centered within the drums it will be difficult or impossible to get the drums over the brake shoes . In most cases the lower brake tracks will be worn to the point that it allows the shoes to drop downward and be WAY out of center . I usually weld the worn dip in the tracks up to the level point and grind smooth for proper fit . This is where the centering tool comes in handy . The centering tool doesn't actually center the shoes but shows where you are at with the tracks. In other words the tool will show whether you need to build up the tracks more or grind them down more to get the shoes centered .


I may be wrong but I don't think that Ford arced the shoes at the factory . I have never had the shoes arced on any of my model A's . The small amount of high spots in the lining will wear down fairly quickly and adjustment will be needed . Arcing can remove a lot of lining in the process .
 
I am sure that Ford never arced shoes at the factory. They're manufactured to fit the new drum when they get to the assembly line. The problems is that the manufacturer of relined brake shoes today doesn't know what drum size they are going to be used on. I have been told that they are usually manufactured to fit a .030 oversize drum and that is what is causing the problem. I would never cut the drums to match the shoes, you might as well saved money and bought used drums to start with.

Charlie Stephens
 
I just did this job on front brakes. After swedging each stud in with the drum bolted up tight through the remaining unswedged stud holes, I still found 0.012 inch wobble inside one drum and 0.008 in the other. This is using a DTI in a lathe to measure.
So I bored both drums true and then found the 12 thou cut one would only just go on over my woven riveted linings, but with too much binding when fitted, and the 8 thou one would not go on at all.
I had firstly hand-filed and sanded the shoes to the correct arcs using a 5 thou feeler gauge before fitting the shoes but, though the arcs were correct, the linings were still to thick.
I did not want to remove the shoes from the hubs to reduce them so filed and sanded them in place by wrapping 80 grit abrasive around them. This did take an hour or so, but I ended up with really great brakes.
This was proven when I went down a very long steep incline in overdrive top and stopped easily at a blocked one-way bridge at the bottom. Others in our group were not so lucky. Bumpers were broken and Armco scarred to avoid head-on collision on the bridge.
This is my experience after fitting many cast iron drums. I have never stopped to see if the drums are round before swedging onto the hubs. The hub flanges are trued before swedging.
SAJ in NZ
 
Really a timely post by those with issues and responses from the experts. I just came in from the garage, attempting to get new riveted linings on my new cast iron drums. And bingo, no fit. I have the backing plate off, with shoes mounted, and the drum is a tight 11 inches. The shoes measure a bit over 11 inches and either the shoes need to be sanded down or as a suggestion in this post string, have the drums turned to fit. (or do both). Also, I am wondering, if anyone has had the experience with bonded linings if bonded linings are thinner negating what some of us are running into with the riveted linings!
 
DHZIEMAN said:
Really a timely post by those with issues and responses from the experts. I just came in from the garage, attempting to get new riveted linings on my new cast iron drums. And bingo, no fit. I have the backing plate off, with shoes mounted, and the drum is a tight 11 inches. The shoes measure a bit over 11 inches and either the shoes need to be sanded down or as a suggestion in this post string, have the drums turned to fit. (or do both). Also, I am wondering, if anyone has had the experience with bonded linings if bonded linings are thinner negating what some of us are running into with the riveted linings!
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Model A brakes are not full floating like newer models . When the lining wears to the point that replacement is necessary, the tracks will usually be worn to the point that they will have to be built up with weld or replaced . The roller pins on the shoe rides on the tracks and as the tracks wear the brake shoes drop down and out of center . When the shoes drop down and out of center , the new unworn lining will be too far down and out of center to allow the brake drum to pass over the relined brake shoes .. Worn tracks will have a worn dip on each side of the tracks that will need to be built up Or the tracks replaced . In most cases , replacing the tracks won't completely solve the problem because the repro part will still have the shoes out of center , Ford understood this fact and didn't offer the tracks alone . In the day , Ford only sold the tracks as a unit already installed on the backing plates . Ford felt that the majority of people wouldn't be able to center the tracks so the final adjustments of the tracks were made at the factory and only sold as a unit with the backing plate for replacement . The average person with some mechanical experience can replace the brake shoes or brake lining on the more modern cars. Model A brakes take a bit more skill and tools to properly fit. Still the model A brakes are very simple .
 
I’m going through the same thing at the moment and intend doing the same as SAJ did to get the hubs on. A little extra time now is a good investment for having a longer future, IMO.
 
DHZIEMAN said:
Really a timely post by those with issues and responses from the experts. I just came in from the garage, attempting to get new riveted linings on my new cast iron drums. And bingo, no fit. I have the backing plate off, with shoes mounted, and the drum is a tight 11 inches. The shoes measure a bit over 11 inches and either the shoes need to be sanded down or as a suggestion in this post string, have the drums turned to fit. (or do both). Also, I am wondering, if anyone has had the experience with bonded linings if bonded linings are thinner negating what some of us are running into with the riveted linings!
Click to expand...
The last thing I would do is turn the drums. Contact a local Model A or V8 club and ask who can arc shoes. Take the shoes back to where you bought them and give them your drum size (have it measured accurately). Remember the drums need to have a small cut to clean them up after they are mounted..

Charlie Stephens
 
Charlie Stephens said:
The last thing I would do is turn the drums. Contact a local Model A or V8 club and ask who can arc shoes. Take the shoes back to where you bought them and give them your drum size (have it measured accurately). Remember the drums need to have a small cut to clean them up after they are mounted..

Charlie Stephens
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I am fortunate! The local auto shop guy has been following with interest all the stuff going on to get brakes on the model A. He can turn them to true them up when I get to that point. Inspection of the roller track shows a lot of wear, Another Local welding shop will get the task of welding some build up on the roller track and I will file down or grind down to size. All doable! Good suggestions to get me going. Thank you all!
 
Charlie Stephens said:
Yes you need to have the shoes arced and maybe a slight cut to true up the drums if this was not done. Have you inquired where you purchased the drums/shoes if they could do the work? Put your general location in your profile and someone might suggest a place to have this done.

Charlie Stephens
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Charlie - Thanks! My Profile shows Sunrise Beach, Mo, which is Central Missouri at Lake of the Ozarks! Will be getting drums trued up locally and go from there!
 
I mad some measurements that confirm what has been said above. The new cast iron drums measure 10.97 inches inside. This means that the inside diameter must be reduced 0.03 inches to reach the original Model A size of 11.000 inches.

I also measured parking brake diameters. The new cast iron diameter measurement is 9.65 inches. I measured an old steel drum that looked like there was essentially no wear on the parking brake drum surface. It was microscopically smaller. This means that one should not turn down the cast iron brake drum part any more than necessary to clean up all the way around. I would not go any deeper than this bare minimum because it would weaken the drum.
 
It sounds like you are on the right track.


A good shop can turn your drums out to 11.000 inches.


You still need to check the fit of the shoes in the finished turned drums to be sure they do not have to be arced. but original shoes with 3/16 thick woven linings should be very close to fitting correctly.


Chris W.
 
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Richard Lorenz said:
I mad some measurements that confirm what has been said above. The new cast iron drums measure 10.97 inches inside. This means that the inside diameter must be reduced 0.03 inches to reach the original Model A size of 11.000 inches.

I also measured parking brake diameters. The new cast iron diameter measurement is 9.65 inches. I measured an old steel drum that looked like there was essentially no wear on the parking brake drum surface. It was microscopically smaller. This means that one should not turn down the cast iron brake drum part any more than necessary to clean up all the way around. I would not go any deeper than this bare minimum because it would weaken the drum.
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Took my drums to a local Machinist! He used is electronic caliper and came up with the same you did, 10.97! One suggestion he made, since I had the hubs swaged into new drums, was to take them to the auto shop and have them put on the drum turning tool and assure the drum was centered on the hub properly, by doing a turn to assure true hub drum centering. I will do that today.
 
DHZIEMAN said:
Really a timely post by those with issues and responses from the experts. I just came in from the garage, attempting to get new riveted linings on my new cast iron drums. And bingo, no fit. I have the backing plate off, with shoes mounted, and the drum is a tight 11 inches. The shoes measure a bit over 11 inches and either the shoes need to be sanded down or as a suggestion in this post string, have the drums turned to fit. (or do both). Also, I am wondering, if anyone has had the experience with bonded linings if bonded linings are thinner negating what some of us are running into with the riveted linings!
Click to expand...

I find as I get older, I should write a checklist of items to be done to install brake shoes properly, and in particular on my Model A Ford! I stated on this post chain, I was having the same problem as another in not getting the brake drum to fit on my new riveted brake shoes. I riveted them so hence, I started there to assure I had chamfered the ends and the rivets were tight and holding the lining tight to the shoe, that I had good springs, the brake floating plate had been welded up to spec and still the drums just would not go over the shoes. Got to looking at the Brake adjuster, ya know that square nut thing to adjust the brake shoes! I had thought I turned it all the way in. I thought! Key words. Since I had the backing plate off the car, I removed the brake shoes, and put the backing plate in a vise with wood blocks so as not to warp anything. Next, I got my home made square wrench and started trying to crank that square nut out more. Started spraying my favorite, WD40, on the adjustment, and just kept working it. Got it to turn freely and it turned several turns. More WD40 and I turned it back in again and then more WD40 and out again and surprise it turned out more. Put the brakes shoes back on the backing plate, by the way I am getting good at putting the springs back on, and the brake drum now fits over the new shoes with a bit of clearance! Gotta start doing check lists, or better yet know more about what I am doing or both! What is left now that I cannot do myself is get the new drums trued to the hub. Should get that done this week when in town.
 
Charlie Stephens ... in So Cal ... or anyone else in the area ... ? It's sunny but chilly day at the top of the Cajon Pass.

Just got a set of front hub/drum assemblies and they measure out to the aforementioned 10.97ish diameter. Close ... but no cigar!


Same 'won't fit' over new shoes issues even though the supplier advertises they are turned after assembly. In my mind that should have meant that they are turned out to minimum 11.00" ... perhaps 11.002".

Anyone have a lead on a place within 30 - 40 miles that have the proper setup to turn Model A hub/drum assemblies?

RS
 
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Charlie Stephens ... in So Cal ... or anyone else ... ? It's sunny but chilly day at the top of the Cajon Pass.

Just got a set of front hub/drum assemblies and they measure out to the aforementioned 10.97ish diameter. Close ... but no cigar!


Same 'won't fit' over new shoes issues even though the supplier advertises they are turned after assembly. If they were? ... in my mind that should have meant that they are turned out to minimum 11.00" ... perhaps 11.002".

Anyone have a lead on a place within 30 - 40 miles that have the proper setup to turn Model A hub/drum assemblies?

RS
 
Any automotive machine shop should be able to turn the front drums, the
rears are the one's that can be a problem.


Bob
 
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