11x3 rear brake drums on A12?

I am still looking into this and have found pics of a unrestored A12 with 11x3 on rear, car has 40k mileage and clip still holding rear drum on axle. Hope to hear from some other owners to see what theirs have. His and mine have same cast number on drums.

Found this on broadcast sheet codes

B28 is 11 x 2.5 brakes
B31 is HD Rear drums..
So is that standard on A12 or a One Of...

For ALL A12's, B31 will be located on line 5 of the broadcast sheet. This decodes as "HD 11" drums, manual adjustment". If the car has 11x3 drums on the rear now, more than likely they are not original factory installed...however, never say never...but unlikely.

Have you decoded the diff to see if it came with the car?

Yes I did years ago. Factory Rear still in car.
I have spoken to two other A12 owners I know in the last few days and both have 11x3 rear.
One is a VERY low mileage car,
Other has been in family since new.

Also heard that they built the first run of A12's with 11x2.5 then later builds had the 11x3's.?

I found the drums and shoes I needed.

After looking online have found people with R/T's having 11x3 rears also.

I hope more owners chime in with what they have on their cars VS what we read they came with.

My '69 A12 Bee had the typical finned 11x2.5 rear drums and 11x3 up front.

Yes B31 is on the broadcast sheet but on line 6 under brakes. Member Lynchroad has all the specs on his post that seem to be on both my A12s Runners, manual brakes. I believe the drums are also finned.

I was searching the web for info regarding my 69 Charger RT's rear brake drums and it lead me to this thread. The car is currently in storage and I am getting parts at this point. I'd like to redo the brakes. Although I don't have easy access to the car I was able to have them email me the attached picture. The drums have a 3641x number on them. The last letter is blurred but is likely an 8, (or maybe a 0 or 6). Doesn't that number mean this car has 11x3 rear brakes? If yes where can I get brake shoes etc as they seem really hard to find.

If I decide to put the correct setup on it instead, I assume that would be 11x2.5 right? since the car has drums all around and is an RT. Does anyone sell a complete 11x2.5 setup to just bolt on and be done? Are there any other concerns I should have if I switch back being what's on there now? Thanks and any advice will be appreciated.

I don't think someone changed the brakes from 11x2.5 to 11x3 as it would require a backing plate change also. Rebuild what is on the car.

What is the build date of the car ?

I will get back to you with the exact build date. The car is a late '68 build. I have general car knowledge .. but am limited when it comes to restoring a car 'correct', so bear with me thanks. I just figured it originally must of had 2.5" rear drums and been swapped simply because that is what so many on forums etc say. That would be great news if the otherwise was true for this car.

The Charger is in storage and hard for me to access, so does that number 36418 shown in the pic definitely mean there are 3" drums in back currently?

my wagner master brake catalog only lists 11x2 1/2" rear drums as available on the charger. the only listing i could find for 11x3" rear drums were for chrysler new yorkers, newports, and imperials. this goes from 1963-1976. if there is indeed 11x3" brakes on your charger, i will have to say they were swapped on from a new yorker or a newport, as the imperial had a 5" bolt pattern. also, my 69 FSM only lists 11x2 1/2" rear drums even on police and heavy[taxi] duty brakes.

Thanks for all your time. But there is still the main question I have that is being lost because of the 'what is factory correct' discussion.

Let me rephrase: I need to order rear brake shoes for the drums on my Charger based on what is on there 'now'. The car is in storage so I must blindly order the shoes etc based on the picture I provided. Are the rear brake drums in my picture with number 36418 11x3 or 11x2.5? Thanks.

i think the number you have on your drum may be a casting # instead of a part #. all the info i have on interchange numbers indicate the 69 charger R/T, coronet R/T, super bee, road runner[with drums], or belvedere, charger and coronet with heavy duty brakes or with trailer towing package had only 11x2 1/2 rear drums. that factory part # is : 2405789.[7 digits] if it indeed has 11x3 drums, it more and more leads me to believe they were swapped. the only way i believe possible to be sure is take the drum off and measure. i know that is not what you want to here, but before you spend the money i believe it's now the only way to be 100% positive. 11x2 1/2" stuff is pretty common [unless you want absolutely NOS parts] as it was used in trucks and vans for many years after the muscle stuff was gone, and is interchangeable. i have done it countless times. i can't say how many vendors chrysler used for their drums, so someone other than me will have to chime in for this info. let us know what you find out.

the alternate part # is 3004933. this is also an 11x2 1/2" drum. this is the drum with cooling fins used in 69-70 on all mentioned above plus fury, GTX, monaco, newport, new yorker, chrysler 300, polara, 70 barracuda, 70 challenger with heavy duty or trailer towing option, 70 cuda, and 70 challenger RT with drum brakes.

OK thanks for your help. I understand you can only give me the info you have and been very nice to provide it. The reason I was hoping to get an answer by using the 36418 casting number was the post below I found on this thread:

================================================
Post:
"So shoes are 2 7/8 wide
drums have a part number 36418 also mwyb5 c21.
Found out they are 11x3 from factory on rear. "

================================================

I was hoping for confirmation being that he has the same casting number as me and he is sure his are 11x3, that would mean mine are that size too. (again remember this is not about if its factory correct or not but instead just what is on my car which I can't access due to it being in storage and need to order brake shoes etc for).

In your opinion, being mine is the same casting number would it likely have to also be the same 11x3 size? (I would assume you can't have the same casting number on 11x3 and 11x2.5 parts, no?) I promise this to be the last question regarding this. Thanks.

don't be afraid of asking questions ! the only "dumb" question is the one not asked ! the 2 7/8" wide dimension gives me reason to wonder because in measuring mopar brake shoe lining for 50+ years, they have all been 2 1/2" or 3" wide. so at 2 7/8", man i don't know. and part numbers are not casting numbers. as to what someone else has on their car, anything is possible. i owned a junk yard from 1970 to 1985, and the ONLY 3" wide drums i came across was on imperials, newports [very rare] wagons with the tow package, and newyorkers. to have you order 3" replacement parts because someone claimed they were factory, i would, in all sincerity, have to have more than one person confirm those were indeed factory installed. if you could round up the necessary parts and find out the drums were 2 1/2" on your car, the backing plates, in my opinion, would really tough to come up with to complete the swap. please keep us updated on this topic. we can all learn from each other. one infamous quote is : "never say never with mopar"....

If I can piggy back on this thread, I'd like to ask another related question. It's actually to do with the 4-wheel HD drums on my '70 Challenger, but I suspect the answer will be the same. Each of my drums have two ports in the back for adjustments. The dust covers were missing on all 4 corners. Has anyone got a pic of what the correct rubber plugs look like?

Like these:

http://www.ebay.com/itm/BRAKE-DRUM-ADJUSTING-HOLE-DUST-COVER-PLUG-RUBBER-/122000811017?hash=item1c67d0a409:g:NKwAAOSwstxVd3E6&vxp=mtr

The picture posted earlier in this thread looks like a standard 11 x 2 1/2" drum.

Thanks, Tman.

CENTRIC 12363016 part is 11" rear drum and friction surface is 2.93 inches wide. Found this part# at Rockauto under 69 Coronet with 440 motor. It is very close to 3 inch wide.

CENTRIC 11103360 brake shoe for 3 inch wide 11" drum. for both front and rear. Found this application under 69 GTX.

There are much more part #s for 11X2.5 drum and shoes though.

So if you definitely need 3" wide drum and shoes, it is available.

Centric # 123.63016 is a 11 x 2 1/2" rear drum.

Centric # 111.03360 is a set of 11 x 3" C/B body front brake shoes and 11 x 3" C body rear brake shoes.

the friction surface of all drums will be wider than the shoe width. note the large rust ridge present when you take drum off to replace parts ? when drums are turned, that ridge becomes part of the "friction surface". a 2.93 friction surface is for 2 1/2" wide brake shoes. 3" wide shoes would lock that drum up solid when the wheel was bolted on no matter how the shoes were adjusted.

edit : brake shoes, as a rule, use the same shoe core for both front and rear applications. that is why there are unused holes and shapes present. "most" shoe material is also the same [unless you are talking a performance shoe from a company that deals with specialty lining], and both sets have a primary[short] and secondary[long] lining, where the primary goes to the front, and the secondary goes to the rear.

I thought some might find this interesting regarding Classic Industries listing some 11x3 rear brake parts for late 60s B-bodies. I just came across this an hour ago.




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