Liberty Rear Disk Brakes for A-Body

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[QUOTE="jos51700, post: 1972243495, member: 10255"

Has anyone figured out how much metal is really being removed?[/QUOTE]

Can someone who has these parts take a measurement of the stock thickness?

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I have an A body 8-3/4 with resplined C body axles in my 68. 10" x 2-1/2" BBP drums.
I'm happy with what I have but always interested in reducing weight and improving performance. If I come across the Liberty parts I may check it out.
 
It's early, and I ain't too bright to begin with, but...

Couldn't you just install the bracket and backing plate for the liberty stuff on top of the axle bearing retainer, instead of under it, and avoid all the custom machined stuff? As long as the backing plates don't hit the p-brake shoes (which could be omitted for an automatic equipped car not driven by Bo or Luke), the plates would just slide out with the axles any time the axles are removed.

Or, couldn't someone just make a longer adjuster, and banish the bracket-milling business?

Don't bash me, I haven't seen the parts personally; just thinking out loud...
 
jos51700 said:
It's early, and I ain't too bright to begin with, but...

Couldn't you just install the bracket and backing plate for the liberty stuff on top of the axle bearing retainer, instead of under it, and avoid all the custom machined stuff? As long as the backing plates don't hit the p-brake shoes (which could be omitted for an automatic equipped car not driven by Bo or Luke), the plates would just slide out with the axles any time the axles are removed.

Or, couldn't someone just make a longer adjuster, and banish the bracket-milling business?

Don't bash me, I haven't seen the parts personally; just thinking out loud...
Click to expand...

As you noted, it would be difficult, if even possible to adjust the axle shaft end play. With the bracket on, the tabs on the adjuster could be too short to reach. This wouldn't be a problem for those using Green bearings, BUT

You would have a spacing problem, in that the thickness of the axle retainer, plus the thickness of the bracket would put the rotor closer to the inboard side of the caliper. My guess is by about 3/8". The rotor wouldn't be centered in the pads, and might contact the parking brake shoes. As you noted, they could be omitted, but many will need an operating parking brake to pass an annual safety inspection. This spacing issue could be overcome by using custom axles with a larger axle offset, the expense of which takes this out of the low-buck swap category. Another possibility would be to use a spacer between the rotor and axle flange, which probably isn't the best idea.

An interesting solution is that of member @blue missile who made spacers to be able to use the stock adjuster and unmachined Cherokee brackets. This solution required axle replacement, too, I believe.
Jeep rear discs on an 8 3/4 axle solution
 
S'cuder said:
As you noted, it would be difficult, if even possible to adjust the axle shaft end play. With the bracket on, the tabs on the adjuster could be too short to reach. This wouldn't be a problem for those using Green bearings, BUT

You would have a spacing problem, in that the thickness of the axle retainer, plus the thickness of the bracket would put the rotor closer to the inboard side of the caliper. My guess is by about 3/8". The rotor wouldn't be centered in the pads, and might contact the parking brake shoes. As you noted, they could be omitted, but many will need an operating parking brake to pass an annual safety inspection. This spacing issue could be overcome by using custom axles with a larger axle offset, the expense of which takes this out of the low-buck swap category. Another possibility would be to use a spacer between the rotor and axle flange, which probably isn't the best idea.

An interesting solution is that of member @blue missile who made spacers to be able to use the stock adjuster and unmachined Cherokee brackets. This solution required axle replacement, too, I believe.
Jeep rear discs on an 8 3/4 axle solution
Click to expand...

Hmmmm....I already have bbp axles, with extra offset for FMJ drums. I wonder how much that extra offset is?
 
jos51700 said:
Hmmmm....I already have bbp axles, with extra offset for FMJ drums. I wonder how much that extra offset is?
Click to expand...

Uh, FMJ drums use the same flange offset as any other BBP axle. And since this disk conversion is for BBP axles anyway, I can’t see there being any difference there.
 
72bluNblu said:
Uh, FMJ drums use the same flange offset as any other BBP axle. And since this disk conversion is for BBP axles anyway, I can’t see there being any difference there.
Click to expand...
It's been ten years since I bought those axles, but I thought that they had a different offset from big car brakes. Beats me. I'm senile!
 
KosmicKuda said:
[QUOTE="jos51700, post: 1972243495, member: 10255"

Has anyone figured out how much metal is really being removed?
Click to expand...

Can someone who has these parts take a measurement of the stock thickness?

*********

I have an A body 8-3/4 with resplined C body axles in my 68. 10" x 2-1/2" BBP drums.
I'm happy with what I have but always interested in reducing weight and improving performance. If I come across the Liberty parts I may check it out.[/QUOTE]

Stock is .25" so you taking it from quarter inch thick to .10 which is equivalent to 12 gauge which is what the drum backing plates are pressed from.
 
I love this kinda stuff. It's true hot rodding. But I still have to ask why people thing a car that hovers around 3K pounds needs 4 wheel discs? I guess it's more of a want/bench racing kinda thing, unless you're doing something where they are actually necessary.
 
Rob in my case I am close to 4K. Made a big difference. Easy as hell to do also, Die grinder, and beer is all that was needed.
 
RustyRatRod said:
I love this kinda stuff. It's true hot rodding. But I still have to ask why people thing a car that hovers around 3K pounds needs 4 wheel discs? I guess it's more of a want/bench racing kinda thing, unless you're doing something where they are actually necessary.
Click to expand...


Im actually doing it on a b body so a little more than 3k but when searching to see if anyone else had done the Liberty swap yet I stumbled on this thread. I picked up the Liberty complete brakes, backing plates, rotors, pads and calipers at pick a part on Saturday for 60.99 so figured its worth a shot.
 
aeonmcallister said:
Im actually doing it on a b body so a little more than 3k but when searching to see if anyone else had done the Liberty swap yet I stumbled on this thread. I picked up the Liberty complete brakes, backing plates, rotors, pads and calipers at pick a part on Saturday for 60.99 so figured its worth a shot.
Click to expand...

Now a b body I can understand a bit more.
 
aeonmcallister said:
Can someone who has these parts take a measurement of the stock thickness?

*********

I have an A body 8-3/4 with resplined C body axles in my 68. 10" x 2-1/2" BBP drums.
I'm happy with what I have but always interested in reducing weight and improving performance. If I come across the Liberty parts I may check it out.

Stock is .25" so you taking it from quarter inch thick to .10 which is equivalent to 12 gauge which is what the drum backing plates are pressed from.
Click to expand...

The stock backing plates are 11 gauge, .1196" thick.

They were also designed to be 11 gauge. The caliper brackets for the Liberty brakes were designed to be ~1/4". There is some kind of reason for that, because if the factory could have cut the amount of material in half they would have to save money.

Now, that reason may not just be the strength of the bracket, but we don't know that. Typically factory parts have a large margin of safety built in, but cutting the bracket thickness by more than half is very significant. Like I said before, maybe it's fine. But unless you're doing an analysis on the strength of those brackets it's all just speculation. Brakes are kinda important, and that's a fair amount of speculation.
 
RustyRatRod said:
I love this kinda stuff. It's true hot rodding. But I still have to ask why people thing a car that hovers around 3K pounds needs 4 wheel discs? I guess it's more of a want/bench racing kinda thing, unless you're doing something where they are actually necessary.
Click to expand...
In that case I’ll definitely be going overkill. I’m planning on doing a 6.4 Hemi swap and when I do I’ll be buying a complete donor car and I’ll be seeing about swapping all the SRT brake stuff over to my Duster. :D I’ll be able to bring the car to a screeching halt by LOOKING at the brake pedal!
:lol:
Then again I’ll have 485hp and maybe some day if I decide to supercharge it I’ll have 600+ to the rear wheels. In that case, those whopping big brakes will come in handy.
 
75slant6 said:
In that case I’ll definitely be going overkill. I’m planning on doing a 6.4 Hemi swap and when I do I’ll be buying a complete donor car and I’ll be seeing about swapping all the SRT brake stuff over to my Duster. :D I’ll be able to bring the car to a screeching halt by LOOKING at the brake pedal!
:lol:
Then again I’ll have 485hp and maybe some day if I decide to supercharge it I’ll have 600+ to the rear wheels. In that case, those whopping big brakes will come in handy.
Click to expand...

Well that's justified.......actually it's all justified. If you have a slant car and want 12 wheel disc brakes, it's justified because that's what you want. On my 64 for example, I plan on a pretty hot 225 later on but the brakes are done. 4 wheel 9" drums. They work well when they're right.
 
RustyRatRod said:
I love this kinda stuff. It's true hot rodding. But I still have to ask why people thing a car that hovers around 3K pounds needs 4 wheel discs? I guess it's more of a want/bench racing kinda thing, unless you're doing something where they are actually necessary.
Click to expand...

For me, I like to reduce unsprung axle weight (all weight, actually) as much as possible, but I also like stock parts over aftermarket if it's something likely to require future service.

That said, I am NOT machining that caliper bracket down to a tenth of an inch. I know that it only sees torsional load, but if that rotor develops any warpage at all, I'd figure the bracket will be fatiguing and breaking in short order. Stamped metal has a much more suitable grain structure for that kinda business, over cast/forged.

This being said, is the caliper being offset by a tenth of an inch (let's assume you're machining only 0.050" off the bracket) that big of a deal? Couldn't you just run a 0.1" spacer under the rotor and call it good, or do I have the assembly backwards in my head?
 
Drum brakes are almost always lighter than their disc counterparts. A LOT of guys down here run them on the dirt track circuit.......and win.
 
RustyRatRod said:
...why people thing a car that hovers around 3K pounds needs 4 wheel discs?.
Click to expand...

Disk's are about more than just stopping power, and rear disk's even more so. Disk's bring the benefit of less fade and make it much easier to modulate braking when traction is limited.

For street driving, I think the biggest disadvantage to drums is the issue of self energizing drums locking up when traction is limited. Lot's of traction? Probably stop well enough - at least once. Not much traction? Better hope the rear drums don't lock up and introduce a dangerous ballet move.
 
DionR said:
Disk's are about more than just stopping power, and rear disk's even more so. Disk's bring the benefit of less fade and make it much easier to modulate braking when traction is limited.

For street driving, I think the biggest disadvantage to drums is the issue of self energizing drums locking up when traction is limited. Lot's of traction? Probably stop well enough - at least once. Not much traction? Better hope the rear drums don't lock up and introduce a dangerous ballet move.
Click to expand...

I go along with some of that but for the most part, it's all in knowing the limitations of the brakes and the car. For instance, with my 64, I don't plan on jackrabbit starts and hard stops. I plan to drive the car like it was intended and what it was intended for. Simple transportation. For that purpose, the drum brakes are just fine.
 
To get rid of the drum brake fade, drill the drums. Get the heat out and they then perform better.
 
RustyRatRod said:
I go along with some of that but for the most part, it's all in knowing the limitations of the brakes and the car. For instance, with my 64, I don't plan on jackrabbit starts and hard stops. I plan to drive the car like it was intended and what it was intended for. Simple transportation. For that purpose, the drum brakes are just fine.
Click to expand...

Knowing the limits of your car is very important, and if you know the limits and drive accordingly that goes a long way.

But, this isn’t the 70’s. Or the 80’s, or even the 90’s for that matter. The vast majority of cars out on the road have disk brakes and ABS at the least, and many now have computer assisted braking. They stop faster and need less driver skill to consistently pull off those short stops. Which means- no matter how well you know the limitations of your car and drive accordingly you’re still at the mercy of everyone else on the road, and they’re not going to drive according to your cars limits. They won’t leave you the stopping distance you need, and ultimately if you hit them when they stop short it’s going to be tough to put the fault on them.

5.7 hemi said:
To get rid of the drum brake fade, drill the drums. Get the heat out and they then perform better.
Click to expand...

You still have the issue of the self adjusters, they don’t necessarily work in unison and their adjustment does vary. So on that day you need to pull off a hard stop you’ll never know if one or both of your rear drums will lock up first because they just clicked over on the star wheel. Disks don’t have that issue, and they’ll give you much more consistent braking.

And drums still won’t work for crap when they’re wet. Maybe not an issue for most A-body’s anymore since they won’t be driven in anything more than minor rain, but it’s something to consider for people that don’t treat their cars like they’ll melt if they get wet.

I still run rear drums, they do get the job done. I did stop backing out of my driveway in the same direction all the time though, because my right rear would always lock up first. Remember the adjusters do their thing in reverse on the brakes, so if you always back and turn the same direction one wheel will always adjust more frequently because it’s traveling further.
 
I hear you and as always my friend, you bring up some great points. Tell you what, you buy me some disc brakes and I'll sling um on. Is that a deal or what? lol
 
5.7 hemi said:
To get rid of the drum brake fade, drill the drums. Get the heat out and they then perform better.
Click to expand...

I have done that before and it works great. Just drill right through into the stopping surface. Done many that way for some of my dirt track friends.
 
I'm always hoping for a realistic opportunity to get rear disks simply from a maintenance standpoint. Pads are SOOO much easier to replace and a whole lot less messy.

I'm very good with drums, but I hate getting all greasy and asbestos-y.
 
Here's a Pic of my newly milled liberty caliper mounts.

DSC_0025.JPG


DSC_0025.JPG
 
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