11 inch backing plate question

[krcevs]

Hi all,
I have a set of 11 inch backing plates for an 8 3/4 rear, but i dont know if they are the 11 x 2 or the 11 x 2 1/2. How do i tell which ones they are?
Any ideas?

Krcevs

 

[5.7 hemi]

I think it's the drum and shoes that dictate what width the brakes are and not the the plates.

 

[moparsteve636]

Thats right! 5.7 The drums and shoes dictate the width.The 3"drums are finned originally.

 

[moparmarks]

Sorry guys but there are different back plates for different width shoes. Otherwise wider shoes would increase rear end width, which they don't. Difference is made up on the inside with the backing plate. Parts books shows different numbers. Books shows that 70-1B's did not come with 11x2, just 11x2.5.
OP I have some 2.5 plates that I can measure the depth.

 

[5.7 hemi]

No ****! I did not know that, but also weren't all rears were 11x2.5 if you had 11 inch drums and the front was 11x3?

 

[moparmarks]

On B-bodies I believe so.
Some C-bodies had 11x2 rears according to the book.

 

[krcevs]

What are the depths for the 11x2 and 11x2 1/2" backing plates?

Krcevs

 

[moparmarks]

I found some 2" plate but haven't found any 2.5" ones. Thought I had some pulled already. Have some still on the axles. Will work on it again this week. I'll atleast get the 2" measurements.

 

[krcevs]

I found some 2" plate but haven't found any 2.5" ones. Thought I had some pulled already. Have some still on the axles. Will work on it again this week. I'll atleast get the 2" measurements.

That would be great! Would you have a set of shoe actuator rods for the wheel cyls? My backing plates are missing them.

Krcevs

 

[moparmarks]

Should have some.

 

[moparmarks]

Well now I'm abit confused. I have a stack of 10x2.5 rear brakes from B-bodies. I have one set of 11x2 that I think are from a truck. Don't have any 11x2.5 that I can find.
Thinking that 11x2.5 never came on a B-body. Even the wagons I've had came with 10x2.5.

 

[696pack]

Well now I'm abit confused. I have a stack of 10x2.5 rear brakes from B-bodies. I have one set of 11x2 that I think are from a truck. Don't have any 11x2.5 that I can find.
Thinking that 11x2.5 never came on a B-body. Even the wagons I've had came with 10x2.5.

There were lots of B bodies that came with 11" X 2.5" rear brakes beginning back in 1966 with the Hemi cars. In 1967 the 440 powered cars had them standard. The below link is from the 1967 Dodge Dealer Data Book.

http://www.hamtramck-historical.com/images/dealerships/DealershipDataBook/1967/67_Coronet0003.jpg

 

[Cranky]

Thats right! 5.7 The drums and shoes dictate the width.The 3"drums are finned originally.

I have a set of 11x2.5 rear drums that are finned and a set of 11x3 fronts that are not finned. I have also pulled 11x2 rear drums off of late 60's pickups.

 

[flypaper]

i have a set of 11x2.5 that came off a 71 sat that was coded for 11' hd brakes
and i also have a 11x2 that came from who knows where?
the drums on the 11x2 are finned also..
i can compare and get measurements
i'm thinking there is a difference between the 2 backing plates

 

[moparmarks]

Fuel pump went out on the Dakota today so I didn't make it to the yard. Here are the brakes that I have.

 

[Moparparts]

Post a close up pic of the inside of your backing plates should know by that

 

[moparmarks]

Well I'm over my brian fart now. Yes those are 11x2.5, duh. Was looking at the wrong B/P. My pile of brakes is a mess. Really need to go through it. Have a stack of the drums but didn't find the B/P yet. Ran out of daylight so will hit it again tomorrow afternoon.

 

[Roadbird]

Well I just found out my 70RR has 12" brake backing plates all around and I have 1 unfinned drum in the front the rest of my drums are missing. I would assume that my Roadrunner came with unfinned brake drums all around. Is this possible? My rearend is 8 3/4 too.

 

[ga66mopar]

Sorry guys but there are different back plates for different width shoes. Otherwise wider shoes would increase rear end width, which they don't. Difference is made up on the inside with the backing plate. Parts books shows different numbers. Books shows that 70-1B's did not come with 11x2, just 11x2.5.
OP I have some 2.5 plates that I can measure the depth.

That makes sense because the axle flange (the drum butts up to the axle flange) and the axle housing flange is the same distance on all 8 3/4. The only way to change the brake shoe width is by off setting the backing plate. Ran into that when I put larger brake shoes on the rear of my 69 dart. I had to change the backing plates as well as the drums.

- - - Updated - - -

Well now I'm abit confused. I have a stack of 10x2.5 rear brakes from B-bodies. I have one set of 11x2 that I think are from a truck. Don't have any 11x2.5 that I can find.
Thinking that 11x2.5 never came on a B-body. Even the wagons I've had came with 10x2.5.

I will take a set of the backing 11x2.5 backing plates if you have any left. I think the bar that goes between the brakes is also specific to the brake shoes size. Meaning the bar for 10 in brake shoes is different then the bar for the 11 in shoes. I need them for my 67 GTX. The rear end got changed.

 

[696pack]

Well I just found out my 70RR has 12" brake backing plates all around and I have 1 unfinned drum in the front the rest of my drums are missing. I would assume that my Roadrunner came with unfinned brake drums all around. Is this possible? My rearend is 8 3/4 too.

Not unless they are aftermarket brakes. No 1970 Mopar had 12" brakes. The backing plates are different from 10" and 11" factory brakes and that is what is being discussed here.