11x3" backing plates??

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abodyjoe

abodyjoe

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how hard is it yo find a clean set of 11x3 backing plates? a friend just hooked me with with brand new set (made in canada) drums and shoes. just need the backing plates.
 
Last edited:
abodyjoe said:
how hard is it yo find a clean set of 11x3 backing plates? a friend just hooked me with with brand new set (made in canada) drums and shoes. just need the backing plates.
Click to expand...
I'm pretty sure the rear backing plates are the same for 2 1/2 drums and 3" drums.

Most likely on any pre-73 C-body .

Here's my rear 11x 2 1/2" assemblies off a 73 New Yorker.

BTW...Factory hand brake cables work perfectly as well.


1763644577032.png



Just for comparison sakes... Here's a pic of the original 10" next to the 11x 2.5 replacements.

The car now stops like someone tied it on !!


1763644667751.png
 

Here are 2 methods of measuring to be sure you get what you are expecting.
(The values do not need to be exact, there is enough difference in each measured value that it will be evident)

Method #1
[FOR SALE] - 10 inch drum backing plates
B, C, E body 5x4.5
1 1/2"=11 x 2
1 3/4"= 10 or 11 x 2 1/2
2" = 11 x 3

A Body
1 5/16" = 10x 1.75



How you measure.

Hang the backing plate off a table so the e brake cable mount does not raise the plate up
PXL_20240710_195516156~2.jpg




PXL_20240710_195528615.jpg



Method #2
(Dimensions from a Hotrod (IIRC) article)
1763651016202.png

​


How to measure
measure as in the photo and add 1.15 for A body and 1.35 for B, C, E body
PXL_20240710_195215327.jpg
 
Thanks Dana for #5.
I have a set of something, now I can check them out.
 
Just looking at the pic the op posted.


If the drum is 11x 2.5, the brake shoe face surface will also be narrower.

The offset of the backing plate for the 11" brakes shouldn't matter.

Unless, of course the inside of the brake shoe is different and offset more into the backing plate.

Probably the reason for the difference in backing plates for 2.5 and 3" brakes.


1763653207463.png
 
Big.J.007 said:
I sold these a few months ago. They were on a 68 plymouth police car with an 8 3/4 rear.

SOLD - Dodge Chrysler Plymouth Mopar 11x3" HD Rear Brake Backing Plates Good Used Look
Click to expand...

thanks.. little too late for me...

i have a set of 2.5" drums, backing plates and shoes that all i would need is the hardware and wheels cyl. a friend gave me the new 3" drums and shoes yesterday so i figured if i could find backing plates i'd just go that route for that little bit more brake shoe. i'd still need to buy hardware and wheel cyl so no big deal. hell the car has 11x2" brakes now that i want to redo and figured lets go bigger while i have it apart. :)
 
As mentioned above , 11 “ x 2 1/2 “ and 11 “ x 3 “ Backing Plates — ARE — Different….

11 “ x 3 “ Rears ( and hence Backing Plates ) were used on Police Cars and Ambulances
And are available — USED ONLY —-

O.P. — Good Luck in the quest / search….

Yours, Craig….
 
mobileparts said:
As mentioned above , 11 “ x 2 1/2 “ and 11 “ x 3 “ Backing Plates — ARE — Different….

11 “ x 3 “ Rears ( and hence Backing Plates ) were used on Police Cars and Ambulances
And are available — USED ONLY —-

O.P. — Good Luck in the quest / search….

Yours, Craig….
Click to expand...
yes, i know they are different then 2.5" and only available used. was just wondering
how hard they are to find these days. maybe I'm better off using the 2.5" stuff i already have.
 
abodyjoe said:
maybe I'm better off using the 2.5" stuff i already have.
Click to expand...
IMHO 10x2.5 would be the way to go as it was designed for the A bodies so factory parts should be easier to obtain and remember
 
Super-Cuda said:
Just looking at the pic the op posted.


If the drum is 11x 2.5, the brake shoe face surface will also be narrower.

The offset of the backing plate for the 11" brakes shouldn't matter.

Unless, of course the inside of the brake shoe is different and offset more into the backing plate.

Probably the reason for the difference in backing plates for 2.5 and 3" brakes.


View attachment 1716480526
Click to expand...

You've got this backward.

The axle flange offset is the same for all BBP axles. The axle width ends up being the same for all the axles that had 11x2", 11x2.5", and 11x3" brakes. Which means that the backing plate offset HAS to be different for each of the different width 11" backing plates. All of the different 11" drum brake widths have to be matched between backing plate, shoes and drums. None of those parts are interchangeable between the different width brakes.

abodyjoe said:
yes, i know they are different then 2.5" and only available used. was just wondering
how hard they are to find these days. maybe I'm better off using the 2.5" stuff i already have.
Click to expand...

I'd be less concerned about finding the backing plates and more concerned about finding another set of shoes or drums if you ever needed them.
 
Dana67Dart said:
IMHO 10x2.5 would be the way to go as it was designed for the A bodies so factory parts should be easier to obtain and remember
Click to expand...

it has a large bolt 8 3/4 in it.. never factory. it also has 11x2" brakes on it now. the shoes are kinda hard to find. i think i'm going to do the 11x2.5" since i already have most of that and its the most common.. i prefer the 11" brakes. i'd go disc but they will move the wheels out and they may hit. don't want that headache.
 
Dana67Dart said:
IMHO 10x2.5 would be the way to go as it was designed for the A bodies so factory parts should be easier to obtain and remember
Click to expand...

Running the 11.75” disks up front with 11x2.5” drums out back works really well. I’ve run that combination on both my Challenger and my Duster, it stops MUCH better than the smaller factory disk/drum set up.

These cars weren’t even designed for radial tires, so the “designed for” argument goes out the window pretty fast when it comes to tires, wheels, brakes and suspension. Adding radials, even narrow ones, significantly changes the grip at the wheels which effects everything else, including the braking.
 
ok. my bad. i misunderstood and never looked when loading the car last night. i think this works out easier anyway.

i believe that these new drums are 11x2.5. can anyone confirm that part number? I'm having trouble finding it.

i also received 11x2.5 shoes and a set of 11x3 shoes.
I'll go with the 11x2 5 since i have the backing plates and now have the shoes. just need wheel cyl and I'll put new hardware in them.

PXL_20251120_175727735.jpg


PXL_20251120_175724637.jpg


PXL_20251120_175716318.jpg
 
Dana67Dart said:
IMHO 10x2.5 would be the way to go as it was designed for the A bodies so factory parts should be easier to obtain and remember
Click to expand...
I think he is using 4.5 bolt circle.

I stand to be corrected on this though.
 
72bluNblu said:
You've got this backward.

The axle flange offset is the same for all BBP axles. The axle width ends up being the same for all the axles that had 11x2", 11x2.5", and 11x3" brakes. Which means that the backing plate offset HAS to be different for each of the different width 11" backing plates. All of the different 11" drum brake widths have to be matched between backing plate, shoes and drums. None of those parts are interchangeable between the different width brakes.



I'd be less concerned about finding the backing plates and more concerned about finding another set of shoes or drums if you ever needed them.
Click to expand...
Thanks for the information.

Hardware kits should be the same though.

Parts are not an issue, at least here in Canada.

I found everything new including the hardware kits at Nappa.

I think Rock Auto also has them.

https://www.napaonline.com/en/search?text=brake+drums&referer=v2&page=3
 
72bluNblu said:
Running the 11.75” disks up front with 11x2.5” drums out back works really well. I’ve run that combination on both my Challenger and my Duster, it stops MUCH better than the smaller factory disk/drum set up.

These cars weren’t even designed for radial tires, so the “designed for” argument goes out the window pretty fast when it comes to tires, wheels, brakes and suspension. Adding radials, even narrow ones, significantly changes the grip at the wheels which effects everything else, including the braking.
Click to expand...


Agreed.

This setup with 11" disks up front and the 11x 2.5" drums in back works fantastic!
 
trucks could have 10 or 11 inch brakes. i try to find the truck plates from 81 up cause they are more likely to have the 11 plates i use. napa brake shoe numbers are as follows:
early pin style shoes for 10 in is ts333
early pin type shoes for 11 in is ts335
later lever style shoes for 10 in are ts445
later lever type shoes for 11 in are ts446
wheel cyl that i use in my kits are 37235 unless the customer wants to match the m/cyl and rear w/cyl
usually anything with an R in part number is a riveted shoe. rock auto has the best price on 10 in drums. unless you get a really good discount at your local auto parts.
 
abodyjoe said:
11.75 up front... the 11" disc work well too but the 11.75 makes quite a bit of a difference..
Click to expand...
You're correct, I meant to say 11.75.

Use the link I sent to contact any Nappa in the USA for the brake parts for your application.

The brake parts in the pic I posted are all from Nappa, including the drums.
 
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