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Rear Disc Brakes

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mrdaud View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mrdaud Quote  Post ReplyReply Direct Link To This Post Topic: Rear Disc Brakes
    Posted: May/15/2022 at 12:51pm
I looked through the forum, but could not find an exact answer to my question.  I have a '69 AMX with front disc/rear drums.  I want to convert the rear to disc.  I don't want Wilwood as they are way too pricey, near the $1000 range.  There appears to be many common rear conversions for GM, Ford, Mopar in the $500 range or less.  Did AMC use off-the-shelf brakes that also fit GM,Ford, etc., that would work on the AMX?  I do have 15" rims that I think are required for disc brakes.  For example, if the rear drums on the AMX were the same as a 6? GM, I should be able to use the conversion kit quoted for the GM.  Anyone know?  Thanks!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ramblinrev Quote  Post ReplyReply Direct Link To This Post Posted: May/15/2022 at 2:43pm
What's the appeal of rear discs? A properly working front disc/rear drum set up is balanced, and stops on a dime.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sonic Silver Quote  Post ReplyReply Direct Link To This Post Posted: May/15/2022 at 3:42pm
Originally posted by ramblinrev ramblinrev wrote:

What's the appeal of rear discs? A properly working front disc/rear drum set up is balanced, and stops on a dime.
I changed out my rear drums to discs on my 70 AMX about 35-40 years ago. I added an adjustable rear brake proportioning valve. I had no emergency brake and saw no advantage in my usage. I changed back to stock after a couple of years.
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Steve_P View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steve_P Quote  Post ReplyReply Direct Link To This Post Posted: May/15/2022 at 4:13pm
The first question is what kind of tires do you have?  If you are not using summer only extreme performance tires, you will gain much more from tires than you will from rear disc brakes.
Discs are obviously superior for cooling if you are road racing.  For a street car, 99.9% of what people have here, rear discs are not needed.  
Yes, I know they are sexy.
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tufcj View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tufcj Quote  Post ReplyReply Direct Link To This Post Posted: May/15/2022 at 4:59pm
These guys make a kit using GM calipers and their own brackets.  I had one of their kits on the rear of my Jeep CJ for years.


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Mopar_guy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mopar_guy Quote  Post ReplyReply Direct Link To This Post Posted: May/15/2022 at 5:05pm
Originally posted by Steve_P Steve_P wrote:

The first question is what kind of tires do you have?  If you are not using summer only extreme performance tires, you will gain much more from tires than you will from rear disc brakes.
Discs are obviously superior for cooling if you are road racing.  For a street car, 99.9% of what people have here, rear discs are not needed.  
Yes, I know they are sexy.

Yep. This right here ^^^^

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mramc View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mramc Quote  Post ReplyReply Direct Link To This Post Posted: May/15/2022 at 5:58pm
Sorta answering the original question 1) The AMC Factory 68/69 Trans-AM Javelins had rear disk brakes fabricated from GM/ Corvette style rear disk brakes set up. Per say never really a "Stock" option.
2) What I did myself was Lincoln Versailles ford nine inch with a new replacement stainless steel disk brake set up. I was all rebuilt and yes it cost at the time . But like I said every thing got rebuilt.
3) There are still Jeep CJ  rear disk brake kits for the Dana 20. They run not a $1k but more like $800 to $700 so  not much cheaper then your $1K price you want to be below. Period AMC built Jeep CJ s used an AMC 20 series rear same as V-8 AMCs . The sticking point of the Jeep CJ kits are the rear axles. You may have to have axle made to fit the AMC car 20 rear end. So not cheap project on any level. The Jeep axles are shorter the the car axles depending on what car you want to put he rear disk brakes on you may have to have axles made. Not cheaper either. Larry Daum
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sonic Silver Quote  Post ReplyReply Direct Link To This Post Posted: May/15/2022 at 7:13pm
I went into my AMC dealer parts department back in about 1971 or 72 and tried to order the rear disc brake setup. The rear discs were listed in the parts book and had to be ordered directly from Ronnie Kaplan (part # 448 5732 and 33).  The guy behind the parts counter told me that I didn't need it, and said it was too expensive. I don't remember how much it was. My guess is that he didn't want to fool with ordering it. Anyway, I didn't order it from AMC, but I put rear discs on my AMX years later. I don't remember where I bought the setup, or what it was sourced from.
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Trader View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: May/15/2022 at 7:45pm
Waste of time and money for anything other then a bracket or full out track car.
I only did this because the Ford 8.8 was the only differential that was economical at the time.
If you like the bling, then spend the money, but your not going to improve on braking performance unless your doing over 120 MPH.
At less then this speed, the rear only provides 20% to 30% of braking. Plenty for the drum brakes to handle.

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mramc View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mramc Quote  Post ReplyReply Direct Link To This Post Posted: May/16/2022 at 5:01pm
The Ford 8.8 is a good choice too. If i was doing a four disk brake setup today this probably be the way to go, for a custom setup. LRDaum
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