Rear drum brakes

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dnicodemus12

dnicodemus12

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Hey guy's, need help. My 1974 Dart 318 has 11 inch drums from the factory. They should have been 10's.They are no good. I need 2 vented 11 inch drums that DO NOT have a raised lip at axle bore. Must be flat across the face. Help!
 
so not like this?
BD8860_1__ra_p.jpg

Perhaps your non stock 11 brakes are 10?
 
I’m agreeing with Pishta that most stock rear drum setups for Dart would have been either 10” or the smaller 9”. Most all of the 10” and 9” aftermarket rear drums are flush/flat (without the flare near the backing plate).

Are you measuring the inside diameter of the drums?
 
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‘74 wouldn’t have 9” drums. As a 318 car it would be front disk so it would also be BBP front and rear.

While the A-bodies were never supposed to come with 11” drums from the factory, this isn’t the first time I’ve heard this. I’ll see if I can find the thread but supposedly there may have been a shortage at one point and some cars may have gotten 11” drums to keep the line rolling. With Ma mopar I’d never say never. It’s also been a long time since 1974 so just because it has them now doesn’t mean they’re factory.

What’s the deal with the “lip” on the drum? If it’s a 5x4.5” bolt pattern mopar axle then any BBP drum should fit with the matching backing plates, 10”, 11”, shouldn’t matter. I put 11x2.5” brakes on all my cars.
 
Found the thread

Rear brake drums

According to this it was a strike, and the brakes used were 11x2”. So, measure your brake shoes. If they’re only 2” wide then you’ll need 11x2” drums, as those backing plates are different than the more popular 11x2.5” so you can’t mix and match drums.

Here’s a link if they are 11x2’s.
Bendix Brakes Brake Drums PDR0187
 
MoparMike1974 said:
Never heard of factory 11" brakes on an A body.
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me neither, but I put them on my 67 barracuda in like 73 or 74. I bought a complete 8-3/4 rr axle out of a late 60's or early 70's b(or c)-body wagon. I sent the axles out to some place in CA, to have the axles shortened and resplined. I adapted the brakes to an a-body 8-3/4. Man with the BBP disks I swapped on the front, and metallic linings all around, that thing stopped like you wouldn't believe! Eventually it ended up on my 74 duster 360. still there.
 
72bluNblu said:
‘74 wouldn’t have 9” drums.
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Uhhh...Yes, they could have.
In 2014 I bought 2 Dart Sports. The '74 had a slant 6 and 4 wheel 9" drums.
Going back further, in 2000 I had a '76 Dart 2 door, slant six 904 stripped down car. Heater and an AM radio seemed to be the only features. 4 wheel 9 inch drums again.
Even further back, in the mid 1990s, I was shooting a couple of movies in Northern CA using a Dodge Dart and a Plymouth Duster for stunt cars. I'd occasionally need control arms and other suspension parts. The Pick N Pull yards still had rows of A body cars then. I recall seeing drum brakes on several '73 and later cars. They were not the majority but they did exist.
A guy on Moparts claimed that there was a Federal law that all cars built in the US had to be equipped with front disc brakes as of January 1 1976. I can't confirm it but it may be true.
 
Kern Dog said:
Uhhh...Yes, they could have.
In 2014 I bought 2 Dart Sports. The '74 had a slant 6 and 4 wheel 9" drums.
Going back further, in 2000 I had a '76 Dart 2 door, slant six 904 stripped down car. Heater and an AM radio seemed to be the only features. 4 wheel 9 inch drums again.
Even further back, in the mid 1990s, I was shooting a couple of movies in Northern CA using a Dodge Dart and a Plymouth Duster for stunt cars. I'd occasionally need control arms and other suspension parts. The Pick N Pull yards still had rows of A body cars then. I recall seeing drum brakes on several '73 and later cars. They were not the majority but they did exist.
A guy on Moparts claimed that there was a Federal law that all cars built in the US had to be equipped with front disc brakes as of January 1 1976. I can't confirm it but it may be true.
Click to expand...

Guess this factory TSB is wrong then? Or maybe you just aren't remembering it correctly. Front 9" drums went away November 1972 for the '73 model year. I was mistaken about the rear 9" drums, those were still around for '74.
Here's the important part
Screen Shot 2020-08-16 at 12.20.21 AM.png

The whole bulletin, No. 05-03-73C
The 1970 Hamtramck Registry "1973 Plymouth, Chrysler & Imperial TSBs" Page

05-03-73C page1.jpg


The '73+, slant 6 cars stayed 4 wheel drum and SBP standard. Front 9" drums went away in '73, only way a '73 had 9" front drums is if it was made before November '72. After that the front drums were 10x2.5" and SBP (those cars also have large ball joint UCA's). All the '73+ V8 cars were front disk, rear drum and were BBP. The slant-6 cars could be had with 4 wheel drums (and were SBP) until January of '76, after that all of them were front disk and BBP. But there were a lot of options even on the slant-6 cars that would trigger front disks, the towing package was one, there were others. My '74 was a factory slant-6, disk brake BBP car and it had very few options.

All of which is irrelevant to this thread, because the OP's V8 '74 would have had front disks, would have been BBP, and would have had 10" (or larger?) brakes.
 
Thanks guys! Great info. We bought Dart new in 74 from Tampa Dodge dealer. Front disc rear drum. Stamping on drums 11.090, made in Canada. Other stampings 80988-10, 55722, and 987. If I put a drum on with a lip at axle bore and tighten lug nuts, it takes the axle shaft end play out and locks up wheel. Acts like an axle shaft puller. That lip CANNOT be there. Tried 7 drums from different mfg. Shoes are 2 inch. This rear end has never been worked on either. All original. Maybe 72bluNblu has the answer.
 
dnicodemus12 said:
If I put a drum on with a lip at axle bore and tighten lug nuts, it takes the axle shaft end play out and locks up wheel
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That sounds like it is hitting the backing plate. I don't see how the lip the projects outword could do what you describe.
 
Dana67Dart said:
That sounds like it is hitting the backing plate. I don't see how the lip the projects outword could do what you describe.
Click to expand...

dnicodemus12 said:
Thanks guys! Great info. We bought Dart new in 74 from Tampa Dodge dealer. Front disc rear drum. Stamping on drums 11.090, made in Canada. Other stampings 80988-10, 55722, and 987. If I put a drum on with a lip at axle bore and tighten lug nuts, it takes the axle shaft end play out and locks up wheel. Acts like an axle shaft puller. That lip CANNOT be there. Tried 7 drums from different mfg. Shoes are 2 inch. This rear end has never been worked on either. All original. Maybe 72bluNblu has the answer.
Click to expand...

I agree with Dana, I’m betting you’ve been getting 11x2.5” drums. The deeper drum hits the backing plate before it bottoms out, and pulls the axle.

The axle flange offset is the same for all BBP drums, so, the backing plate offset has to be different for different widths. So the backing plate for an 11x2.5” drum has more offset than for an 11x2”. The 11x2’s are harder to find, and I would bet money most parts shops aren’t giving you a C-body or truck 11” drum, which is where most of the 11x2’s were used originally. If you aren’t careful it’s easy to get an 11x2.5”.
 
dnicodemus12 said:
Thanks guys! Great info. We bought Dart new in 74 from Tampa Dodge dealer. Front disc rear drum. Stamping on drums 11.090, made in Canada. Other stampings 80988-10, 55722, and 987. If I put a drum on with a lip at axle bore and tighten lug nuts, it takes the axle shaft end play out and locks up wheel. Acts like an axle shaft puller. That lip CANNOT be there. Tried 7 drums from different mfg. Shoes are 2 inch. This rear end has never been worked on either. All original. Maybe 72bluNblu has the answer.
Click to expand...

Maybe try grinding off or milling the protruding lip. If it makes a difference, great - if it doesn't, then no harm no foul - - and on to next idea. :)
 
72bluNblu said:
Guess this factory TSB is wrong then? Or maybe you just aren't remembering it correctly. Front 9" drums went away November 1972 for the '73 model year. I was mistaken about the rear 9" drums, those were still around for '74.
Here's the important part
View attachment 1715578942
The whole bulletin, No. 05-03-73C
The 1970 Hamtramck Registry "1973 Plymouth, Chrysler & Imperial TSBs" Page

View attachment 1715578941

The '73+, slant 6 cars stayed 4 wheel drum and SBP standard. Front 9" drums went away in '73, only way a '73 had 9" front drums is if it was made before November '72. After that the front drums were 10x2.5" and SBP (those cars also have large ball joint UCA's). All the '73+ V8 cars were front disk, rear drum and were BBP. The slant-6 cars could be had with 4 wheel drums (and were SBP) until January of '76, after that all of them were front disk and BBP. But there were a lot of options even on the slant-6 cars that would trigger front disks, the towing package was one, there were others. My '74 was a factory slant-6, disk brake BBP car and it had very few options.

All of which is irrelevant to this thread, because the OP's V8 '74 would have had front disks, would have been BBP, and would have had 10" (or larger?) brakes.
Click to expand...
Despite your ego, you are not always right. Ma Mopar was known for some oddities through the years.
 
72bluNblu said:
I agree with Dana, I’m betting you’ve been getting 11x2.5” drums. The deeper drum hits the backing plate before it bottoms out, and pulls the axle.

The axle flange offset is the same for all BBP drums, so, the backing plate offset has to be different for different widths. So the backing plate for an 11x2.5” drum has more offset than for an 11x2”. The 11x2’s are harder to find, and I would bet money most parts shops aren’t giving you a C-body or truck 11” drum, which is where most of the 11x2’s were used originally. If you aren’t careful it’s easy to get an 11x2.5”.
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So, once again I remove old drum. Measured the depth inside where the 2 inch shoes contact. Measures 2 1/2". Tells me these original drums are 11x2.5". Backing plate shouldn't be an issue. I'm trying to replace them because they've been turned past safe limits. I've ordered a couple 11x2 so in a few days I'll know.
 
Kern Dog said:
Despite your ego, you are not always right. Ma Mopar was known for some oddities through the years.
Click to expand...

My ego? Buddy you're the one arguing about a car that was 40 years old when you bought it being 100% factory original despite your complete lack of historical info on the car. If it was a '73 I'd say it's possible. A '74? Unlikely. A '76? Sorry pal. The factory TSB covers it. And that's not a factory brochure printed before production started, that's a TSB for the factory mechanics. If anything the date on that was probably later than the swap over actually started to cover any possibility of the earlier brakes being used. Sure, engine blocks were put into production years after they were cast, it's been documented. But your argument is that a bunch of later cars got earlier brakes years after the brakes were discontinued, and that you found several of them spanning several years? Those cars would also have needed to have the small ball joint UCA's. It's not a single part like an engine block, running those 9" front drums requires a 9" spindle, different wheel bearings, the small upper ball joint upper control arms that also went away for the '73 model year, all of it. Nope, not buying it.

I mean, I saw a Fiero with a Lambo kit at a wrecking yard once, but I'm not gonna say it came that way from the factory. Lots of things happen. Drag racers switched disk cars to drums back in the '70's because they thought the pad knock-back would slow them down. Guys pull disk brakes and later model K frame's from donors and roll their early suspension underneath before then send it to the scrapper. Happens all the time with the '73+ cars when they're used for donors.

dnicodemus12 said:
So, once again I remove old drum. Measured the depth inside where the 2 inch shoes contact. Measures 2 1/2". Tells me these original drums are 11x2.5". Backing plate shouldn't be an issue. I'm trying to replace them because they've been turned past safe limits. I've ordered a couple 11x2 so in a few days I'll know.
Click to expand...

The machined depth on an 11x2.5" drum is actually 3", so, if your drum measures 2.5" deep it's an 11x2", not an 11x2.5".

The only way an 11x2.5" drum will fit is with an 11x2.5" backing plate, it will not physically fit with an 11x2" backing plate because the 11x2" backing plate has a shallower offset back from the axle.
 
And when you put that 2.5" drum onto the studs, and push it on, the rim of the drum will hit the 2.0 backing plate showing a large gap between the back of the drum-face and the axle flange. If you look for it, I think you can see it. If not, you can tell it's wrong because the hub-centering ring on the axle, is not protruding thru the hole in the drum correctly.
There is no cure for this other than to use matching parts.

But here's the wildcard;
If the shoes are too wide, the backside of the drum faces might hit the edges of the shoes first,lol, even if the drums and backing plates ARE matching.. That is why the shoe width is about .5 less than the drum depth.
 
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72bluNblu said:
My ego? Buddy you're the one arguing about a car that was 40 years old when you bought it.
I mean, I saw a Fiero with a Lambo kit at a wrecking yard once, but I'm not gonna say it came that way from the factory. Lots of things happen. Drag racers switched disk cars to drums back in the '70's because they thought the pad knock-back would slow them down. Guys pull disk brakes and later model K frame's from donors and roll their early suspension underneath before then send it to the scrapper. Happens all the time with the '73+ cars.
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I admit that you do have some knowledge but you aren't old enough to have seen these cars when they were new. For that matter, neither was I...at least I wasn't old enough to work on them then. You can't argue what you didn't see.
My point....
There were some strange things done back then.
Sure, the scenario you presented above is plausible and likely. I still say to have seen as many 9" drum brake cars as I used to see adds at least some doubt to your absolutes.
 
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