Rear Brake Dilemma

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GlennB4u

GlennB4u

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I have a strange question. Recently, I started making my way to the brakes on my 67 Barracuda. I decided to redo them completely. When I pulled off the rear wheels, I saw something pretty strange (see pics). The car has 11inch rear drums on it and that caught me by surprise. But that's not the only thing, there were washers set behind the drum to keep it from rubbing the backing plate ....strange. My question is this... How can I tell what's supposed to be on this car?
The images can be seen here --> http://gdw-stuff.com/barracuda/?p=593
 
If is equipted with eleven inch drums I guess that is fine. Maybe wrong drums like off a b-body. If the drums have a readable part number try to figure out what they belong on.
 
FWIW, I bought a set of new drums for my 10 inch brakes and they rubbed the backing plates. I figured it was just poor quality control. I ground the lip on my backing plate down a bit.
 
I'd do the opposite. Turn the back edge off the drums, assuming the inner face of the drum does not hit the outer edge of the shoes.
 
I see on your web page that you may want to go back to smaller drums. Let me know if you positively identify what housing and backing plates you have. I may be up to a swap,if your diff is an 8 3/4.
 
magnumdart said:
I see on your web page that you may want to go back to smaller drums. Let me know if you positively identify what housing and backing plates you have. I may be up to a swap,if your diff is an 8 3/4.
Click to expand...

Yes, it's an 8 3/4 489 housing... I just find this scenario strange.
 
Measure the width of your shoes and their diameter. They will either be 1 7/8" or 2 1/2" wide and should be 10" in diameter. Those drums are 11" large bolt pattern that have been redrilled for small bolt pattern. When you try to find 10"X1 7/8" small bolt pattern drums you'll know why you have those cobbled up drums.
 
Yup, turn back drum lip so it sits without the washer as it is lifting the drum off the axle register and making the fit sloppy. Or just get 10's but that requires more parts.
 
SirDan said:
FWIW, I bought a set of new drums for my 10 inch brakes and they rubbed the backing plates. I figured it was just poor quality control. I ground the lip on my backing plate down a bit.
Click to expand...
I bet you got front drums. I ordered 10" drums off rockauto that appeared to be described as "rear" (a bit confusing), but got front drums. I can buy those all day cheap, the SBP rears are un-obtanium. It appears one could cut the lip off front drums to fit the rear. Sounds like you figured that out, except you cut the backing plate lip (I wouldn't).
 
I think the same thing has happened to me with buying 10" drums from Rockauto. It described them as rear but they are rubbing the backing plates when installed.
I guess I can "shim" with some washers but think getting the lip cut down would be best.
Anyone know how much they need to be cut down?
 
It's hard to tell from the TINY pictures posted on your webpage, but at the very least those are the wrong drums for the backing plates you have. None of those pictures zoom, only the thumbnails actually load.

If I had to hazard a guess, someone did a BBP conversion on your car and used 11" backing plates. But, those backing plates are specific to the size drum they're for. BBP 11" rear drums came in 11x2", 11x2.5", and 11x3", and you CAN NOT mix and match the backing plates and drums between those sets. The BBP axles all have the same flange offset from the housing, so therefore the backing plates do not for the different width brakes.

It's also hard to tell, but if your axles are A-body axles that were re-drilled to 5x4.5" then you still actually have to use SBP brakes, just with the drums re-drilled to 5x4.5. The axle flange offset is different going from SBP to BBP brakes. I don't think that's what's going on because of the diameter of the axle flange in the pictures, but they're small pictures.

Somewhere on here there's a thread that lists the various offsets of the BBP backing plates to identify which ones you have, I'll see if I can find it.
 
Used to be able to click on my tiny pictures to expose huge ones...I'll have to look into that.

My axles are SBP and the drums have been drilled for that so they have both patterns...I'm thinking of just going with new axles with a BBP.
 
GlennB4u said:
Used to be able to click on my tiny pictures to expose huge ones...I'll have to look into that.

My axles are SBP and the drums have been drilled for that so they have both patterns...I'm thinking of just going with new axles with a BBP.
Click to expand...

The axles are SBP? Well, that's your problem. :banghead:

They never made SBP 11" rear drums. So, you have 11" BBP drums and backing plates that were drilled for SBP. Problem is, as I mentioned above, SBP axles and BBP axles do not have the same flange to housing offset. Which is why you have those "spacers" on your studs.

Yikes. #-o

So, the good news is that you can probably just re-use the brakes you have (without the spacers!) if you buy a set of BBP axles.
 
This is a touch off topic, but here is the solution I used for 11" drums that bound up when torqued. The Chinese measure in metric, and we use inches. I fear they round off the conversions and then nothing works. This is the thread in B-bodies only.

http://www.forbbodiesonly.com/moparforum/showthread.php?75332-11-3-drums

The finished surface width represents the friction surface not the ID of the drum.
 
magnumdart said:
This is a touch off topic, but here is the solution I used for 11" drums that bound up when torqued. The Chinese measure in metric, and we use inches. I fear they round off the conversions and then nothing works. This is the thread in B-bodies only.

http://www.forbbodiesonly.com/moparforum/showthread.php?75332-11-3-drums

The finished surface width represents the friction surface not the ID of the drum.
Click to expand...

So that thread is about front drums, since you're talking about ball joint clearance. And it sounds like you may have had a hub mismatch?

I've bought a couple new sets of the 11x2.5" heavy duty finned drums, and they've all cleared the backing plates for the rear axle.

This one is pretty obviously the SBP axles being mated to BBP drums, that just doesn't work.
 
Generally speaking the /6 cars got 9" drum brakes and the V-8 cars got 10" brakes.
Since that is the case, an 11" brake drum had to be drilled for a 4" bolt pattern to fit on an A-body axle. Or, the axle has been converted to BBP. It's not a problem unless the front has not been converted and the problem is carrying spare tires to support the car.
 
I bought the Rock auto drums, and had the edge and the flange both cut 1/8 inch. Fit great, but also have them turned at the same time. Mine were out of round.
 
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