Liberty Rear Disk Brakes for A-Body

-
RLF Cuda

RLF Cuda

Barracuda Bob
FABO Gold Member
Joined
Jan 7, 2012
Messages
265
Reaction score
352
Location
Aurora, CO
I am researching the rear disk brake conversion shown in Mopar Action August 2018 issue. The conversion looks like it will work as stated and give great low cost brakes with reduced weight.
I currently run B-Body drums, 11x3", so they are heavy but do work well. The front brakes are the late B-Body police disk brakes with pin calipers, 11 3/4" diameter. These are excellent brakes with manual master cylinder.
The Liberty rear mount for the calipers are $13 each at LKQ Pick-A-Part in Denver area. Rock Auto has an excellent PowerStop Caliper-Rotor-Pad package with drilled and slotted rotors for $226.79 (KC 219736). The more expensive issue is machining the support to 0.100" thickness on a Bridgeport Mill. I have located a shop that will do this work but need to bring in the parts to get a cost estimate. That I will do soon. Attached is a photo of the Liberty rear brake assembly.
Next issue of Mopar Action will address plumbing and emergency brake issues. I don't know how complex this will be, but Richard Ehrenberg generally has practical solutions to these problems. Glad he is on our side!
This conversion should cost ~$300 when complete. If you use the Liberty caliper/rotor from a boneyard, the cost will be even less. Caliper rebuild kits (seal and boot) are a few bucks. Caliper mounting hardware a few bucks more. This could be a very low cost conversion to modern rear disk brakes.

20180713_130031.jpg
 
Mopar axle flanges apparently have remained unchanged for years. The Liberty flange bolt pattern should work for 8 1/4, 8 3/4, 9 1/4 and Dana rear ends. What needs to be addressed is the off-set of the mount to account for different axle flange dimensions. I hope M/A addresses this question in the next article.
 
Jeep Cherokee rear disks are a bolt on for a 8 1/4, no machine work. Won't work on 8 3/4 though, because the bearing is held in by a plate, and the cherokee mount is to small in the center, and also too thick.
 
Dont tell my Cuda that....it seams pretty happy with the cherokee discs on its 8.75.
 
mbaird said:
Dont tell my Cuda that....it seams pretty happy with the cherokee discs on its 8.75.
Click to expand...
DO tell! With factory tapered bearings and all? It would be interesting to see how you got it to work
 
Green Bearings...
I shimmed the disc hat with a spacer and enlarged the hole in the backing plate so it would slide over the bearing.
I havent tried it on factory bearing but I think if you were to press the bearings off then put backing plate on and press the bearing back on it might work.

My conclusion after all this work is that I dont drive fast enough to need anything more than 4 wheel drums...lol

The 4 sp Swinger I am building will get factory drums with smaller bore master.
 
mbaird said:
Dont tell my Cuda that....it seams pretty happy with the cherokee discs on its 8.75.
Click to expand...
You're fine. Unless you are really USING your brakes. But the Liberty brakes use thicker/better rotors.
 
what part needs machined down to .1 of an inch?

That seems pretty thin.
 
Just purchased the entire rear disk brake system from a 2007 Liberty for $60 at U Pull And Pay in Denver. The brakes looked like they were recently done, so I may use them as is. I will reseal them just to be sure. The mounts are 4 bolt but the same pattern as the 8-3/4 5 bolt so a new hole needs to be drilled. This should be easy. There is plenty of room for machining the back to get the desired centering. I will wait for the Mopar Action article next month to see what is needed. The parking brake arrangement is very simple, so I hope adapting this to the existing Cuda system is easy. MA usually has good fixes.

As for using Green Bearing, I would never touch them. I got less than 500 miles on the set I used on my car years ago. They simply cannot handle side loads and destroy themselves when used for cornering. The tapered roller bearings are best. The Liberty axles are held in place with C-Clips, so they have at least 0.005" freeplay. Probably more. And they work well with sliding caliper disk brakes, so a 8-3/4 set up with 0.003" end play should be fine with these calipers.
 
RLF Cuda said:
As for using Green Bearing, I would never touch them. I got less than 500 miles on the set I used on my car years ago. They simply cannot handle side loads and destroy themselves when used for cornering.
Click to expand...

YEARS AGO are the 2 key words in that statement. The green bearings have been updated and a lot of people are running them on a lot of cars in a lot of different situations without issue. Ask Cass (Dr. Diff) about them.
 
I would be good to have some solid information on Green Bearings. Especially how the design changed to improve bearing life. Having a product fail early in its introduction is bad for image. So my experience Early On keeps me from even thinking about them. I would also like Richard Ehernberg's input before I would consider them in any application.
 
RLF Cuda said:
I would be good to have some solid information on Green Bearings. Especially how the design changed to improve bearing life. Having a product fail early in its introduction is bad for image. So my experience Early On keeps me from even thinking about them. I would also like Richard Ehernberg's input before I would consider them in any application.
Click to expand...

DoctorDiff did a little write up on his blog about the difference in the new “green” bearings, and why the old ones used to fail.

Why Green Bearings? - Quality Body Shop Drivetrain

I personally still prefer the tapered bearings. There are pros/cons to each kind, just like anything.

As for Ehrenberg, while I think he definitely has made some really useful contributions, I personally don’t blindly trust his opinions without an independent fact check after his whole “ball joint overangling” BS in his “disk-o-tech” article about using the F/M/J/B/R spindles on an A body. It was total speculation on his part, and he published it without ever bothering to check the actual suspension geometry that results. Of course it turned out he was completely wrong about it, the suspension geometry change you get by using FMJ spindles on an A body are both minor and arguably beneficial depending on how your car is set up.

I’ll have to take a look at the Liberty rear disk conversion. Ehrenberg tends to come off as a bit of a purist (just my opinion), so I’m a little surprised he’s doing a rear disk conversion. Machining brake parts down to a tenth of an inch thick seems a bit marginal if they’re parts that see braking load. But I haven’t seen the coversion so maybe it’s no big deal. I’ll have to take a look at the article.
 
Mopar Action Oct 2018 issue just came out with the final details of the rear disk brake instillation. Most of the details are straight forward. Need to find a 3/8"-24 to SAE (JIC)3/16" 37° flair fitting. But that should be easy to locate. Jegs/Summit have the fitting in 3/8" to AN3. I need to find out if this is correct. I also want to look into using the factory rubber brake hose vs new lines and fittings. I need to get some hoses to check this out.
MA also has a somewhat hokey emergency brake cable arrangement what I think/hope can be done better. Again, I need to get some junkyard cables and check out a few things to see if there is a neater/cleaner way to do this.
I also want to mock up the brakes to the axle and be sure that the cut they recommend is correct.
I already have a rear proportioning valve on my car so that parts isn't needed.
I have to also check my stud length. I have truck axles that were resplined to the right length for the A-Body housing width. That was done in the early '90's and I don't think those axles are to be found anymore.
So it may take some time to find out what issue I run into, but I will post my experiences when I learn something. Tomorrow I hope to take the 'Cuda to Bandimere for "Test&Tune". I am running OLD BFG Radial T/A's that have no traction, so I don't expect to go better than 14.70's. Altitude at Bandimere also hurts as altitude correction is often 7700 feet +/- a few thousand feed. Now that hurts power!
Bob
 
72Dart6pack said:
Go with Doctor Diff stuff & be done with it. Why screw around?
Click to expand...

oldkimmer said:
$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
Click to expand...

Sometimes it’s better to just pay the money up front. Read about all the issues people have with the cheaper eBay kits. Read about this whole Liberty brake conversion. Spend a day in the junk yard looking for parts. Disassemble those parts, clean them up, take them to a machinist to have them turned down. Spend another day fitting everything, making some kind of custom bracket for the brake cables, etc.

What’s your time worth? Assuming you do all the junk yard diving and don’t buy new parts, you save a few hundred bucks maybe? Assuming you get good useable parts from the yard. But you spend a couple of days screwing around looking for parts, running back and forth to the machine shop, test fitting everything, etc.

Sure, the Dr. Diff stuff is more expensive, but it fits, it works great, and everything you need comes straight from him and can be installed in a few hours. I’ve done my share of wrecking yard parts pulling, I’ve cheaped out and bought crappy internet kits, and I’ve installed Dr. Diffs kits too. I send Cass the money now and don’t look back, my time is worth more than that.
 
"The Liberty rear mount for the calipers are $13 each at LKQ Pick-A-Part in Denver area". I did a bit of digging and can't find much for the parking brake backing plates. If someone can get those for me I'd pay them for their time and shipping. Grab the parking brake hardware and parking brake shoes too.
 
cawcislo said:
"The Liberty rear mount for the calipers are $13 each at LKQ Pick-A-Part in Denver area". I did a bit of digging and can't find much for the parking brake backing plates. If someone can get those for me I'd pay them for their time and shipping. Grab the parking brake hardware and parking brake shoes too.
Click to expand...

You should go start a wanted ad in the classified section

Thanx
 
mbaird said:
Dont tell my Cuda that....it seams pretty happy with the cherokee discs on its 8.75.
Click to expand...

Pics? Could probably be done to tapered bearing axles with similar machining as is done to the liberty stuff

75slant6 said:
YEARS AGO are the 2 key words in that statement. The green bearings have been updated and a lot of people are running them on a lot of cars in a lot of different situations without issue. Ask Cass (Dr. Diff) about them.
Click to expand...

Maybe don't ask the guy selling them.

RLF Cuda said:
I would be good to have some solid information on Green Bearings. Especially how the design changed to improve bearing life. Having a product fail early in its introduction is bad for image. So my experience Early On keeps me from even thinking about them. I would also like Richard Ehernberg's input before I would consider them in any application.
Click to expand...

He'll tell you straight up: great for drag -only.

72bluNblu said:
As for Ehrenberg, while I think he definitely has made some really useful contributions, I personally don’t blindly trust his opinions without an independent fact check after his whole “ball joint overangling” BS in his “disk-o-tech” article about using the F/M/J/B/R spindles on an A body. It was total speculation on his part, and he published it without ever bothering to check the actual suspension geometry that results.
Click to expand...

Generally agree with you but in the ORIGINAL article, he was clear that they might but it was unproven.
And given the availability of parts then, there was no reason to scrounge fmj stuff. Nowadays, I still wouldn't use FMJ because I'm a purist but impirical evidence is hard to argue with.

Regarding the liberty swap, I don't like machining the mount that thin but if it's forged it's probably ok. I realize it sees only torsional load, but that's still pretty thin. I have wide offset axles for bbp and fmj rear drums and wonder if I could go thicker on that flange.

I don't like the hokey e'brake setup and don't see why they could just drill a hole in the liberty linkage arm, and I don't car for the lack of hoses. Couldn't you just use the liberty hose and adapt it to hard line somewhere along the axle?

I do like the Mopar bloodline, commonly available parts, and 24 pound weight saving (hellloooooo drilled and slotted rotors? )

Any one else heard any simple walk around these problems?
 
You must log in or register to reply here.
-

Back
Top