bigger rear drums

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7demon2

7demon2

Registered User #1824
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i have seen alot of threads on here for disc brake conversions. i have seen little talk of the back brakes on here. i figure to change over to the big bolt pattern in the fall. in doing so i figured i would upgrade my back brakes while i was at it. i have the factory drums on my 72 now 10 by 2 1/2 inch. can the 11 by 2 1/2 inch drum setup fit with the 14 inch rallyes? i figured i look for a 70 thru 74 imperial , newyorker or fullsize wagon, and grab the whole back brake setup. i will get new axles from mosler. will this work? are there any drawbacks with this setup?
 
I don't know about the rallyes but 11" brakes off of a Dodge pickup is another place to look. I have actually put the 11" stuff off of a 9-1/4 out of a Ramcharger and it bolted right on my 8-3/4"
 
340mopar that is another place i hadn't thought of looking. i know alot of the big c body cars have them, but i hadn't given any thought to a truck.what year was it do you remember? thanks
 
I had a '75 pickup with a 9-1/4" with 11" brakes that I removed to put in and 8-3/4" that had 10" brakes I just swapped all of the brake stuff. It worked fine. If I remember correctly the 9-1/4" only uses 4 bolts on the axle plates but the 5th bottom bolt like on the 8-3/4" was already in the backing plate it just was not used.
 
that is good to know. i was going to ask about that 5th bolt on the backing plate, but you beat me to it! thanks again! :thumblef: do you remember if it made a big difference in brakeing?
 
Not to hijack this thread, but had a question....On the topic of rear drums. How are the rear brakes measured anyway to determine the size? (9, 10 or 11") Sounds like a stupid question but I have a couple pairs of backing plates only that are bare. Do you just measure the diameter of the backing plate? What measurment do you actually take to determine what you have?.....Sorry bout' this. Thanks.

:book:
 
i belive you take a measurement across the drum, but don't quoate me on this.
 
7demon2 said:
i belive you take a measurement across the drum, but don't quoate me on this.
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Thats what I was thinking but I do not have any drums to measure. Thats why I was unsure. I just have the backing plates kickin' around.
 
I spoke with someone at Layson's Restoration and the gentleman there informed me that all 7 1/4 thru 9 1/4 rear brake sets interchange. I have tried it and used truck stuff as well as wagon rear brakes for my 8 3/4 axles.
 
Drum brake backing plates have three "pads" on each side that the shoes rest on. I would hazard a guess that by measuring this distance from side to side should give you a pretty close idea as to the drum size.

Revhendo
 
7demon2 said:
that is good to know. i was going to ask about that 5th bolt on the backing plate, but you beat me to it! thanks again! :thumblef: do you remember if it made a big difference in brakeing?
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The truck was an old Forest Service truck that is why it had the 11" brakes. Since it originally came with the 11" brakes and I never drove it with 10" I do not know if there is any difference. Trucks don't have much rear brake bias anyway because the are so light in the back that the 11' brakes probably don't make much difference on a truck unless you were towing. Bigger brakes won't heat up as fast as a smaller brakes will. It will take less pedal effort to slow down or stop with bigger brakes than it would will smaller brakes because they have more friction area. So if you have to have manual brakes because of a large cam you would want bigger brakes so you would not have to push as hard to stop the car as you would with smaller brakes. I still have the 9" drums and my Valiant that runs low 11's at 120ish and I can fool around to stop the car. I have to jump right on them and have to push damn hard to get it to slow down. It's not scary are anything, I just have to PUSH!
 
416demon said:
I spoke with someone at Layson's Restoration and the gentleman there informed me that all 7 1/4 thru 9 1/4 rear brake sets interchange. I have tried it and used truck stuff as well as wagon rear brakes for my 8 3/4 axles.
Click to expand...
there is a fact worth noteing! thanks 416demon!
 
That government stuff is weird. The truck was a '75 D100 shortbed wide side. 318, 727, power disc brakes, manual steering, A/C, 9 1/4", 3.55 w/sure grip & 11" brakes, 16" wheels. Oh, and of course that cool pastel green exterior w/ white interior.
I converted the truck to a 360, 904, power steering, 8 3/4 3.23 w/sure grip, black interior, white exterior, lowered. sold it 8 years ago.
I still have the original 318 and the 727 is in my '65 Valiant I drag race.
 
340mopar i am very familiar with the forestry trucks. i am a member of the 1947- 1998 classic chevy and gmc board. the forestry division made some wierd trucks. mostly used 1 ton setups. they made 3 and 4 and 6 door trucks from as far back as early 60's! not too many of those babies around anymore though.
 
Just a thought, so reply at will (not trying to be an *ss). On cars, especially performance cars with the disc/drum set-up is it not detrimental to put those huge, heavy drums on the back? More weight to get and keep rolling, then more rotating mass to slow down? Front brakes do 70-80% of the braking and under hard braking the rear lifts-so they would lock up faster and easier theoretically :wack: . The few times I've had to do "Oh,sh*t" stops on the Dart's 10" drums, it always wanted to swing to the right. I was told to leave the 10" drums on, put the 11 3/4" rotors up front, and dial in the proportioning for best results. Like I said, not trying to be rude, just want people's thoughts and experiences.
 
i suppose in theory on the performance aspect of rolling weight and mass you are right. i also suppose in theory the drawbacks on the rear drums being bigger than the front disc (brakeing)you are right again. it is a judgement call i guess. an adjustable portion valve is the key here.....
 
14 inch will fit. I have 11" from a 68 fury on my 8 1/4. It came that way and i left them on there. I have the valve cranked down to correct the rear locking.

You are correct your front does the majority of the stopping on the front. Why do people spend high dollars on rear disc setups ? I'll never know. The reason I have the 11" on mine is they came with the rear.

7demon4, Is that the stovebolt your refering to? If so Im member 10050 same username just add a 0
 
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