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Do ZJ discs need a bigger master cylinder?

G

gcam

NAXJA Forum User
Location
alberta, canada
I've read some stuff now on ZJ disc brake conversions for the 8.25 from the sites listed below.

My one concern is this... Calipers require more fluid than wheel cylinders do. None of these guys have swapped in bigger master cylinders to accomodate this, at least they don't mention anything about it. By comparison, M.O.R.E. strongly suggests upgrading to a ZJ master cylinder when swapping in a Ford 8.8 rear axle to accomodate the disc brakes.

I know there are a bunch of guys here that have done thie ZJ rear disc swap. Do you have to swap in a bigger master cylinder to make this work.

Geoff

http://geocities.com/dcpaschal/mitch02.html

http://home.swbell.net/rriojas3/reardisk.html

http://www.naxja.org/forum/showthre...light=ZJ+brakes
 
Only some rear discs need a bigger master if the piston has a larger CC area than the wheel cylinder it is replacing. The ZJ ones are not bigger and carry the same part number for the master as the XJ does. The proportioning valve however is a different part number but not sure if that is because the mount is different or the spring pressure inside. I swapped to the ZJ one but have not noticed a real difference but it should only make a difference under emergency braking which is hard to judge. I had to do one the other day and it pulled up nice and straight and no lock up front or rear so happy enough.
 
OK, I'm going to look like a dummy here.... What do you mean a bigger CC area?

Is the ZJ proportioning valve a direct swap?

Thanks,
Geoff
 
gcam said:
OK, I'm going to look like a dummy here.... What do you mean a bigger CC area?

Is the ZJ proportioning valve a direct swap?

Thanks,
Geoff
Click to expand...

I believe CC means Carbon Copy :D

I ran with my stock 92 MC for about 4 years with the ZJ rears and no issues good stopping power, I recently swapped in the dual dia booster which made a huge difference
 
IIRC, there was a change in the MC in 1996-1997 (1995?) time frame. If you have the latter you may not have to do anything with the MC.

I may be recalling this incorrectly so if anyone knows better please speak up.

r@m
 
gcam said:
OK, I'm going to look like a dummy here.... What do you mean a bigger CC area?

Is the ZJ proportioning valve a direct swap?

Thanks,
Geoff
Click to expand...

He he, no I meant cubic centimetres. As in the volume comparison between the wheel cylinder in the drum and the piston in the caliper.

As for the p/valve, see how I changed it on my site. www.go.jeep-xj.info
 
Root Moose said:
IIRC, there was a change in the MC in 1996-1997 (1995?) time frame. If you have the latter you may not have to do anything with the MC.

I may be recalling this incorrectly so if anyone knows better please speak up.

r@m
Click to expand...

From 95-up all the XJ's went to a dual diaphram booster but they were used on XJ's from 92-94 with the ABS option.
 
gcam said:
Is the ZJ proportioning valve a direct swap?

Thanks,
Geoff
Click to expand...

Well sort of. Since the ZJ has ABS there is only one line coming out for the front brake circuit vs. the two on yours. You could just tee off for the other one. I have friends that used the ZJ one on their TJ's (37" tires and Explorer discs) and say it works great for them. If you wanted a direct swap I'd suggest getting part # 56052227AA which is for a 04 TJ Unlimited with disc brakes. The mounting bracket would have to be modified but the lines will all connect just like the one you have.
 
MJR said:
Well sort of. Since the ZJ has ABS there is only one line coming out for the front brake circuit vs. the two on yours. You could just tee off for the other one. I have friends that used the ZJ one on their TJ's (37" tires and Explorer discs) and say it works great for them. If you wanted a direct swap I'd suggest getting part # 56052227AA which is for a 04 TJ Unlimited with disc brakes. The mounting bracket would have to be modified but the lines will all connect just like the one you have.
Click to expand...

You dont have to tee off for the extra fron line at all. They use the same housing and just have a plug where the extra line runs on the non ABS Jeeps. Just screw it out and fit the one off your old one and you are done like I showed in the write up.
 
Gojeep said:
You dont have to tee off for the extra fron line at all. They use the same housing and just have a plug where the extra line runs on the non ABS Jeeps. Just screw it out and fit the one off your old one and you are done like I showed in the write up.
Click to expand...

Makes it easier.
 
I am thinking of converting to discs, question:
Is there any way to modify the ZJ emergency brake cables to use them on the XJ?
 
falcon556 said:
'96, D35, 4.0, ABS.
Click to expand...

They would be too short because of the location of the adjuster. On the 97-up only the left cable would work. You would have to use a longer cable and might have to extend the adjuster rod which is covered in this article http://www.4x4wire.com/jeep/tech/brakes/xjhoseext02/ . The cables you might need to use are either from the TJ-L (about 7 1/4" longer) or the KJ (about 37 1/4" longer) ones.
 
MJR said:
They would be too short because of the location of the adjuster. On the 97-up only the left cable would work. You would have to use a longer cable and might have to extend the adjuster rod which is covered in this article http://www.4x4wire.com/jeep/tech/brakes/xjhoseext02/ . The cables you might need to use are either from the TJ-L (about 7 1/4" longer) or the KJ (about 37 1/4" longer) ones.
Click to expand...

I like the extended rod solution.
Thanks.
 
MJR said:
They would be too short because of the location of the adjuster. On the 97-up only the left cable would work. You would have to use a longer cable and might have to extend the adjuster rod which is covered in this article http://www.4x4wire.com/jeep/tech/brakes/xjhoseext02/ . The cables you might need to use are either from the TJ-L (about 7 1/4" longer) or the KJ (about 37 1/4" longer) ones.
Click to expand...

Doesn't that only matter if you've got a lift kit on though?
 
Chancer said:
Doesn't that only matter if you've got a lift kit on though?
Click to expand...

No because although the TJ/ZJ have the e-brake adjuster located similiar to a 84-96 XJ except the XJ one is a foot or two forward of them. After more thought there is another reason. The adjuster ends are different also. The TJ/ZJ and 97-01 XJ have a adjuster assembly that has the cables mounted a few inches apart and the 84-96 XJ's have them spaced a lot further. To make them work would require a fair amount of fab work (either extending the adjuster all the way to the rear of the floor tunnel and moving/adding new cable mounts or some how making a ZJ/TJ/97-01 XJ e-brake and adjuster work at the rear of the floor tunnel).
 
MJR said:
No because although the TJ/ZJ have the e-brake adjuster located similiar to a 84-96 XJ except the XJ one is a foot or two forward of them. After more thought there is another reason. The adjuster ends are different also. The TJ/ZJ and 97-01 XJ have a adjuster assembly that has the cables mounted a few inches apart and the 84-96 XJ's have them spaced a lot further. To make them work would require a fair amount of fab work (either extending the adjuster all the way to the rear of the floor tunnel and moving/adding new cable mounts or some how making a ZJ/TJ/97-01 XJ e-brake and adjuster work at the rear of the floor tunnel).
Click to expand...

Another possibility would be to make a little metal tab that fits on the emergency brake hook on one side and a cable slug on the other, use the XJ cable, shorten it a little and go to a sailboat place (they deal with cables) to get a slug or ball swaged.
Another would be to just loop the existing cable over the hook, use a thimble to protect the cable, a U clamp to secure it until I am sure of the proper length, then swage it.
I am starting to pick the parts, I got the proportioning valve from one place for $25 (too much) and ordered the calipers, brackets and shields for $30 at another place.
I plan to use new rotors about $21 each.
 
falcon556 said:
Another would be to just loop the existing cable over the hook, use a thimble to protect the cable, a U clamp to secure it until I am sure of the proper length, then swage it.
You mean like this?

zjcable.jpg
Click to expand...
Click to expand...
 
Gojeep said:
falcon556 said:
Another would be to just loop the existing cable over the hook, use a thimble to protect the cable, a U clamp to secure it until I am sure of the proper length, then swage it.
You mean like this?

zjcable.jpg
Click to expand...

Close, that would be what I'd do to find the right length, after that I'd crimp the two ends together permanently, with a thimble (inner liner) in the loop to protect the cable.
This is just a thought, still hoping to adapt ZJ cables. Today I bought a M8 x 1.25 coupling nut and some 8mm threaded rod plus a couple of plain nuts to explore extending the parking brake rod to make up for the ZJ cable length.
At this point I have everything I need except time and availability of my XJ.
In the mean time I will listen, read and get ideas.
There are two things that I am not completely satisfied with, the ebrake and the brake hose location.
Click to expand...
Click to expand...
 
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