Rear 20 Disc Upgrade - JeepForum.com

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post #1 of 67 Old 08-20-2009, 09:05 PM Thread Starter
cjlevoy
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Rear 20 Disc Upgrade

Sitting around the campfire one night, my buddy and I started discussing on upgrading our rear drums to rear disc. At first thought it doesn't seem to be to difficult. But Has anybody tried to accomplish this without using the kits that are available. As 800 bucks is hard to come by these days. If you have what all parts did you have to find? do you need to change the proportioning valve and master cylinder? Any info would be great.


82scrambler
258 /W EFI
twinsticked 300
4.56s locked front and rear
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post #2 of 67 Old 08-20-2009, 09:37 PM
string
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did you try to search?
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post #3 of 67 Old 08-20-2009, 10:01 PM
Totallymetal
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I am putting Nissan Maxima calipers with cable actuated emergency brakes on homemade brackets and Samurai disks on very shortly. Not my idea, pretty popular DIY that you can find with search. Actually the original recipe was calling for 300zx calipers, but the Maxima(96) donor I found measures out exactly the same. As far as proportioning valve and MC. I am going to try it 'as is' for now and see how it acts, I have a 1 ton Chevy hydroboost I will be putting together in a few weeks (months).


2007 JK Rubicon
5.5 Rock Krawler X-factor lift w/37 x 12.5 x 17 BFG KM2s, 5.13 Superior gears
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post #4 of 67 Old 08-20-2009, 10:10 PM
1986cj
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post #5 of 67 Old 08-21-2009, 07:32 AM
foggybottombob
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The first picture is 300ZX calipers on the scout Dana 44 axle on the rear of my CJ7.
The second pic is the part set for the same calipers to go on the rear XJ Dana 44 on my XJ.




The parts you need are these:

(2) 87 300 ZX calipers - junkyard $32
Geo Tracker 2dr thin rotors 89-98 $48
discard thickness 0.315
nominal thickness is 0.394
caliper brackets $35
87 300 ZX brake pads (2) pairs $35
10 dorman 610358 lugs $32.53
4 grade 8 metric bolts $15
6 grade 8 axle retainer bolts $24
two bearing preload spacers $10
parts for e-brake cables $15

All this adds up to about $250. You need to shorten the hard lines on the rear axle by 4" on each end. I used a double flare tool to just cut off the ones I had and make new ends. I hacksawed off the little bracket which holds the ZX caliper hose from the car in the junkyard. Then I welded that little bracket on my axle to hold the caliper hose. That saved me from having to make a brake hose bracket. And get the little clip that holds the hose to the bracket too. I made an e-brake cable holder out of pipe and washers. The last thing I did was put some 1/4" plate under the brake lines where they pass under my spring perches as a skid plate to keep the lines from being cut if the spring perch came down on a rock off road somewhere. I had to drill my rotors to 17/32" to fit the dorman lugs I bought. You need longer lugs because the rotors are thicker than the brake drum backing plate they are replacing. And I put my calipers on where the e-brake lever is at the top. When I bleed these I have to unbolt them from the bracket and turn the assembly so that the calipers are on top of the rotor so that the air will bleed out. I've been using this for about 6 months now and it works great. The ebrake works too. Since the piston is small for the ZX caliper, you do not have to change the CJ proportioning valve from stock for this rear disc setup.

Now the guy I got the brackets from has done this same thing for his AMC 20 axle. He made brackets and wheel bearing preload spacers for me. You need the spacers to compensate for the fact that you have taken out the brake drum backing plate. You can make your own by cutting up your backing plate. I bought some from a guy named Chris. You can contact Chris about buying brackets at this address:
bsteel1002@qwestoffice.com

Last edited by foggybottombob; 08-21-2009 at 07:45 AM.
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post #6 of 67 Old 08-21-2009, 08:06 AM
ACAD_Cowboy
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Just a follow on for those who may be unable to find a Z-car:

Cardone Friction Choice Brake Caliper-Rear
Part No. 19-1220
Reman.; w/Installation Hardware; Right; OE Metal Piston;Supplied w/o Mounting Bracket
112.99 w/ 35.00 core


Cardone Friction Choice Brake Caliper-Rear
Part No. 19-1221
Reman.; w/Installation Hardware; Left; OE Metal Piston;Supplied w/o Mounting Bracket
112.99 w/ 35.00 core

Wearever Brake Rotor - Front
Part No. YH141710
Front 2 Door
20.99

Wagner BRAKE ROTOR
Part No. BD61936
2 Dr.
32.99

Wearever Silver Brake Pads/Shoes - Rear
Part No. NAD 272
Pad; Organic; OE Replacement
15.99

Wagner Brake Pads/Shoes - Rear
Part No. PD272
Pads; ThermoQuiet; OE Replacement; Organic
35.49

These are the web pricing from advance auto, your local pricing may vary.
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post #7 of 67 Old 08-21-2009, 08:12 AM
foggybottombob
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I found that you can buy new GEO Tracker rotors cheaper than you can get a junkyard rotor and have it turned. So don't go hunting rotors in the junkyard. It's not worth the effort.
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post #8 of 67 Old 08-21-2009, 08:19 AM
ACAD_Cowboy
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Follow on #2

Earlier Z-car calipers, circa 1984

Cardone Friction Choice Brake Caliper-Rear
Part No. 19-686
Reman.; w/Installation Hardware; Right; OE Metal Piston;Supplied w/o Mounting Bracket
86.99 w/ 25.00 core

Cardone Friction Choice Brake Caliper-Rear
Part No. 19-687
Reman.; w/Installation Hardware; Left; OE Metal Piston;Supplied w/o Mounting Bracket
86.99 w/ 25.00 core
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post #9 of 67 Old 08-21-2009, 04:38 PM Thread Starter
cjlevoy
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Posts: 22
Thanks for all info. i shouldbeable to start putting together a stuff.

82scrambler
258 /W EFI
twinsticked 300
4.56s locked front and rear
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post #10 of 67 Old 08-22-2009, 09:35 AM
ACAD_Cowboy
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Drafters do it in excruciating detail. I found a PDF in one of the link showing the caliper mounting plate details but found it would be a nightmare for a layman to try to layout and cut. So for anyone who is interested, I can hook you up with both a print copy and a DXF file for use with CNC Laser, CNC Plasma or CNC Router. I Could probably also supply a plywood buck for those who are in the building phase and need templates.
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post #11 of 67 Old 09-02-2009, 07:08 PM
CJman77
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Quote:
Originally Posted by foggybottombob View Post
The first picture is 300ZX calipers on the scout Dana 44 axle on the rear of my CJ7.
The second pic is the part set for the same calipers to go on the rear XJ Dana 44 on my XJ.




The parts you need are these:

(2) 87 300 ZX calipers - junkyard $32
Geo Tracker 2dr thin rotors 89-98 $48
discard thickness 0.315
nominal thickness is 0.394
caliper brackets $35
87 300 ZX brake pads (2) pairs $35
10 dorman 610358 lugs $32.53
4 grade 8 metric bolts $15
6 grade 8 axle retainer bolts $24
two bearing preload spacers $10
parts for e-brake cables $15

All this adds up to about $250. You need to shorten the hard lines on the rear axle by 4" on each end. I used a double flare tool to just cut off the ones I had and make new ends. I hacksawed off the little bracket which holds the ZX caliper hose from the car in the junkyard. Then I welded that little bracket on my axle to hold the caliper hose. That saved me from having to make a brake hose bracket. And get the little clip that holds the hose to the bracket too. I made an e-brake cable holder out of pipe and washers. The last thing I did was put some 1/4" plate under the brake lines where they pass under my spring perches as a skid plate to keep the lines from being cut if the spring perch came down on a rock off road somewhere. I had to drill my rotors to 17/32" to fit the dorman lugs I bought. You need longer lugs because the rotors are thicker than the brake drum backing plate they are replacing. And I put my calipers on where the e-brake lever is at the top. When I bleed these I have to unbolt them from the bracket and turn the assembly so that the calipers are on top of the rotor so that the air will bleed out. I've been using this for about 6 months now and it works great. The ebrake works too. Since the piston is small for the ZX caliper, you do not have to change the CJ proportioning valve from stock for this rear disc setup.

Now the guy I got the brackets from has done this same thing for his AMC 20 axle. He made brackets and wheel bearing preload spacers for me. You need the spacers to compensate for the fact that you have taken out the brake drum backing plate. You can make your own by cutting up your backing plate. I bought some from a guy named Chris. You can contact Chris about buying brackets at this address:
bsteel1002@qwestoffice.com
Do you have any pics from the other side of the brake? I am curious to see more to better understand what your meaning by some of this stuff. I wanna do this.

Brian
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post #12 of 67 Old 09-03-2009, 08:09 AM
foggybottombob
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Those are all the pictures I have. There are 4 main elements.
1) Calipers
2) Caliper mounting brackets
3) Rotors
4) Bearing preload spacers

The only non-obvious one is the last item. When you have drum brakes you have a backing plate that holds the brake shoes etc. That plate is made of 11 gauge steel. I don't remember what the thickness but I figured out that it was 11 gauge. Since the backing plate is between the axle flange and the axle retainer it is a spacer between the retainer and the bearing inside the axle tube at the outer end of the tube. When you remove that backing plate you have to replace the function of being a "spacer" that it provided. The rings you see in my picture are what I used for that. I am not familiar with an AMC 20 but if it uses axle retainers to hold the axle in then it will need these substitute wheel bearing pre-load spacers. If you do not have spacers on such an axle, then you will be tightening down too hard on the wheel bearings when you bolt the shaft in. If you have anymore questions you can PM me.

I'm going out of town to wheel in west CO all weekend so I'll be away from the computer for a few days.
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post #13 of 67 Old 09-19-2009, 10:22 AM
Totallymetal
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There is something I noticed by using the Maxima bracket and caliper rather than 300ZX. In the photo you can see the adapter plate has space at the top of it, that's where the 300ZX bracket bolts to. The Maxima bracket is a bit lower on the adapter. I am glad I didn't drill the holes prior to fitting it up.

BTW I am using the original proportioning valve and it is fine.




2007 JK Rubicon
5.5 Rock Krawler X-factor lift w/37 x 12.5 x 17 BFG KM2s, 5.13 Superior gears
Warn Powerplant HD

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post #14 of 67 Old 09-20-2009, 11:48 AM
ACAD_Cowboy
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Would it be too much to ask for the location of the holes against the 300ZX caliper mounts? Since I have nice print of the 300ZX I'd like to add the optional holes for the maxima for the data file.

Also, do you have any specs on your bearing pre-load ring?

-= Francis =-

These, in the day when heaven was falling, The hour when earth's foundations fled, Followed their mercenary calling, And took their wages, and are dead.

Their shoulders held the sky suspended; They stood, and earth's foundations stay; What God abandoned, these defended, And saved the sum of things for pay.

A.E. Housman
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post #15 of 67 Old 09-20-2009, 12:36 PM
Totallymetal
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I have to take it apart again to replace bearing and seal, since I didn't remove the thrust block. I will put the adapter on top of the scaled to size template I used and get some measurements and post them up.

When you say beariing pre-load ring I assume you are talking about the shimming to replace the drum brake backing plate. I just cut the original backing plate and used it. I can measure it's thickness if that's what you need.

This is the front side if anyone wants to see it for reference. I haven't sorted out the emergency brake yet. I think it's going to be pretty simple.


2007 JK Rubicon
5.5 Rock Krawler X-factor lift w/37 x 12.5 x 17 BFG KM2s, 5.13 Superior gears
Warn Powerplant HD

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