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View Full Version : WJ ZJ or KJ disc conversion


kss3369
September 30th, 2017, 19:26
I've finished my 4.5 lift and running 33's. I want to improve the braking performance. I've seen WJ and ZJ disc brake conversions. What are the differences? And what if I want to do to a WJ in the front next?

Kittrell
September 30th, 2017, 19:58
WJ brake conversion is for the front, KJ and ZJ are for the rear and are essentially the same thing. You will get far more performance out of the WJ front conversion than you will out of a rear disc conversion. It also has the benefit of cross over steering.

Jeep Driver
October 1st, 2017, 06:56
WJ brake conversion is for the front, KJ and ZJ are for the rear and are essentially the same thing. You will get far more performance out of the WJ front conversion than you will out of a rear disc conversion. It also has the benefit of cross over steering.

I'll disagree with that statement.

KJ swap was the best move I made, until now.

Can't wait to get the fronts installed and I'm ordering the rears this week. I passed on the WJ.........just not where I wanted to go, ultimately.

http://i.imgur.com/tagW067h.jpg (https://imgur.com/tagW067)

Hypoid
October 1st, 2017, 09:46
I'll disagree with that statement.

KJ swap was the best move I made, until now.

Can't wait to get the fronts installed and I'm ordering the rears this week. I passed on the WJ.........just not where I wanted to go, ultimately.

http://i.imgur.com/tagW067h.jpg (https://imgur.com/tagW067)

What is your projected cost for that set-up? Does that cost include replacing the stock steering?

RCP Phx
October 1st, 2017, 10:32
What is your projected cost for that set-up? Does that cost include replacing the stock steering?

Expensive, not including the spindle conversion! It uses early factory YJ knuckles so no steering changes. It also has about the same piston area as the WJ calipers!
http://www.wilwood.com/BrakeKits/BrakeKitsProdFront.aspx?itemno=140-12576-DR&year=2000&make=Jeep&model=Cherokee&option=Req.+conversion+to+87-89+YJ+front+spindles

whitexj98
October 1st, 2017, 10:47
I'll disagree with that statement.

KJ swap was the best move I made, until now.

Can't wait to get the fronts installed and I'm ordering the rears this week. I passed on the WJ.........just not where I wanted to go, ultimately.
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Fresh drum brakes adjusted correctly are pretty much the same as kj/ zj rear disk brakes IMO. Most people praise fresh rear disk brakes as superior to wore out drums.

Having done both front WJ and rear ZJ. Fronts will be noticeable improvement in braking..

sinat01
October 1st, 2017, 11:59
The simple fact that I wouldn't have to adjust drum brakes anymore is plenty enough reason to switch to KJ brakes on the rear. that and easier maintenance. only trouble im having with the KJ swap is finding the backing plate studs, as the ones that came off the donor were too rusted and new ones from the dealer are $12 each.

Bent
October 1st, 2017, 12:20
The simple fact that I wouldn't have to adjust drum brakes anymore is plenty enough reason to switch to KJ brakes on the rear. that and easier maintenance. only trouble im having with the KJ swap is finding the backing plate studs, as the ones that came off the donor were too rusted and new ones from the dealer are $12 each.
Have you looked at an online factory parts retailer for the plate studs?

RCP Phx
October 1st, 2017, 12:27
Look no further...... http://www.currieenterprises.com/CE-2012

whitexj98
October 1st, 2017, 14:05
I just grabbed some 3/8 grade 8 bolts from Lowe's.

sinat01
October 1st, 2017, 17:10
Those T-bolts work good?

Jeep Driver
October 1st, 2017, 17:41
What is your projected cost for that set-up? Does that cost include replacing the stock steering?

$1250 for the front and $850 for the rear.

Front cost includes braided lines, and unit bearings. Rear includes braided lines and parking brake.


As for a comparison to the WJ??????
Virtually every high-end build is running Baer, Wilwood, or Brembo.........not WJ brakes.

I have high expectations.

trippled
October 1st, 2017, 19:08
WJ brake conversion is for the front, KJ and ZJ are for the rear and are essentially the same thing. You will get far more performance out of the WJ front conversion than you will out of a rear disc conversion. It also has the benefit of cross over steering.

Ill disagree as well. After 3 axles and countless parts, swapping to rear discs made a huge improvement. I went with a rear disc 8.8. to me, going from drums to discs is like going from a carb to EFI. Sure it works but it's antiqued tech.

Green XJ Jeep
October 1st, 2017, 21:37
Fresh drum brakes adjusted correctly are pretty much the same as kj/ zj rear disk brakes IMO. Most people praise fresh rear disk brakes as superior to wore out drums.

Having done both front WJ and rear ZJ. Fronts will be noticeable improvement in braking..

Less fade, better heat dissipation, superior wet weather performance, self cleaning, ease of maintenance and adjusting, better bias from front to rear and side to side all make rear discs far superior to drum any day of the week.

Sure fresh drum bakes might be equal to discs in your opinion but what about when the drums start to wear, or get wet, muddy, hot, or out of adjustment? Which all will happen.
You cant honestly say that the performance for the life of the discs are going to fluctuate and change as much as the drum set up.

IMO rear discs should always be swapped before doing a WJ swap.

clydefrog
October 1st, 2017, 22:00
I've finished my 4.5 lift and running 33's. I want to improve the braking performance. I've seen WJ and ZJ disc brake conversions. What are the differences? And what if I want to do to a WJ in the front next?
I love how no one has answered your question.
What are the differences?
Assuming your asking what the change is as compared to stock. I cant speak, I haven't done the WJ swap. Just amused at the ensuing arguments over drums, disc and what not. I too am curious as to what kind of change could be expected from a WJ front swap.

whitexj98
October 2nd, 2017, 04:36
I love how no one has answered your question.
.

The very first response answered the questions.

Less fade, better heat dissipation, superior wet weather performance, self cleaning, ease of maintenance and adjusting, better bias from front to rear and side to side all make rear discs far superior to drum any day of the week.

Sure fresh drum bakes might be equal to discs in your opinion but what about when the drums start to wear, or get wet, muddy, hot, or out of adjustment? Which all will happen.
You cant honestly say that the performance for the life of the discs are going to fluctuate and change as much as the drum set up.

IMO rear discs should always be swapped before doing a WJ swap.

Have you done both?

Green XJ Jeep
October 2nd, 2017, 07:23
The very first response answered the questions.



Have you done both?

Agreed the first response answered it pretty well.

Yes I have done both and probably will not do a WJ swap again.
IMO the money is better spent elsewhere especially since I have no intentions of ever running a tire bigger than 33"s and a brake line upgrade and yellow stuff pads work just fine for me.

Jeep Driver
October 2nd, 2017, 15:24
The very first response answered the questions.



Have you done both?

No it did not.

WJ brakes are the byproduct of steering and TB geometry........that is the job at hand.

I would love to have crossover steering, but not at the expense of braking and not at the expense of TB geometry.

Can I fabricate? sure. Can I cobble something up for braking? possibly.


I've been through EVERY freak'n WJ thread, read every word, learned from every mistake others have made..........seen every F'n hack job too.
To get the TB right takes a lot of work and some sacrifice of other parts and arrangements such as sway bar mounts........just not worth if for me. Others done the full WJ axle swap to get there.............

If you think WJ brakes are a bolt-on wonderment............dream on.

whitexj98
October 3rd, 2017, 05:05
No it did not.

WJ brakes are the byproduct of steering and TB geometry........that is the job at hand.

I would love to have crossover steering, but not at the expense of braking and not at the expense of TB geometry.

Can I fabricate? sure. Can I cobble something up for braking? possibly.


I've been through EVERY freak'n WJ thread, read every word, learned from every mistake others have made..........seen every F'n hack job too.
To get the TB right takes a lot of work and some sacrifice of other parts and arrangements such as sway bar mounts........just not worth if for me. Others done the full WJ axle swap to get there.............

If you think WJ brakes are a bolt-on wonderment............dream on.

The OP asked a simple question as to what the differences were and it was answered. Not sure where you got that WJ was bolt on....

WJ swap has many advantages, one of the top mods I have done to my jeep, only downside is the short track bar but any crossover steering puts the track bar in the same place, unless you start doing more custom fab.

You have more into rear disk brakes then a WJ swap, what are your expected results/ use for your jeep? I could care less how much someone spends on mods, but for a decent wheeler on a Dana 30, high end, one off brakes seems silly... I mean its an XJ.

RCP Phx
October 3rd, 2017, 10:10
I'll answer the OP with real numbers............

The XJ and the ZJ share the same front brakes...11" diameter non-ventilated rotors and single piston calipers.
The WJ front brakes are 12" diameter "ventilated" rotor and dual piston calipers(and much larger brake pads).

The ZJ and the KJ share similar rear brake components (except the KJ is a direct fit for the CHRY 8.25 axle)...11.22" non-ventilated rotor with a single piston caliper

RCP Phx
October 3rd, 2017, 10:17
As for a comparison to the WJ??????
Virtually every high-end build is running Baer, Wilwood, or Brembo.........not WJ brakes.

I have high expectations.

All you've done is make trail repairs impossible with "not readily" available parts! Your braking will be about the same.

No it did not.

WJ brakes are the byproduct of steering and TB geometry........that is the job at hand.

I would love to have crossover steering, but not at the expense of braking and not at the expense of TB geometry.

Can I fabricate? sure. Can I cobble something up for braking? possibly.


I've been through EVERY freak'n WJ thread, read every word, learned from every mistake others have made..........seen every F'n hack job too.
To get the TB right takes a lot of work and some sacrifice of other parts and arrangements such as sway bar mounts........just not worth if for me. Others done the full WJ axle swap to get there.............

If you think WJ brakes are a bolt-on wonderment............dream on.

Or you can just not do anything with the steering! When I did my WJ brakes I had no intention of re-doing my steering( I did just upgrade to the Currie Correctlink).

Green XJ Jeep
October 3rd, 2017, 11:27
All you've done is make trail repairs impossible with "not readily" available parts! Your braking will be about the same

There are some parts your not exactly going to get at the local napa with a wj swap either

RCP Phx
October 3rd, 2017, 11:29
There are some parts your not exactly going to get at the local napa with a wj swap either

Name one part that can't be purchased anywhere OTC!

Green XJ Jeep
October 3rd, 2017, 15:27
Name one part that can't be purchased anywhere OTC!

Rotors. Unless of course you are running 2 different lug patterns

RCP Phx
October 3rd, 2017, 17:01
Rotors. Unless of course you are running 2 different lug patterns

But at least you can buy it! It only takes 15 minutes and a drill to fix the pattern issue. It doesn't have to be accurate since the rotor is "hub-centric". If "push came to shove", you could use a KJ rotor!