Okay so i did the rear disc brakes swap and prop valve. My problem is that when i press the brake the rear locks up on wet roads while the front does not. Is this normal?

 

sounds like what was possible when i was reading about doing that.

 

That's not normal, or very safe. Are you sure the proportioning valve was plumbed in correctly? Just wondering.

 

i put it in the way it came out of the zj
is there a specific way to plumb it
it only happens under hard breaking if that matters

 

I've never done your particular swap and don't know what's supposed to be included in it. I was just wondering. Was the master cylinder part of the swap?
I know on some other vehicles when switching from front discs/rear drums to 4 wheel discs you usually use the master from the donor vehicle.
I know it's a totally different type of vehicle, but when I installed 4 wheel discs on my Omni's I had to get the master cylinder that was for a 4 wheel disc brake system from a Daytona.
This may or may not apply here though, but since you have premature rear lockup something is wrong. I'm just trying to figure out what it is.

 

i switched the master cylinder out after the swap and it did it before and after

 

when i did my swap, i used the master cylinder and booster from a 2000 cherokee and just changed the spring in the proportioning valve. my rears would lock just before the front but only under hard braking on dry surfaces. since i did the wj front brakes, that no longer happens. you just need more power in the front.

zedpapa

 

Now that makes total sense. Thanks for posting. It's much clearer now.

 

ok thanks for the input ill have to do the wj braking upgrade

 

i think ol'blue is saying i didn't help. i went back and read it again. yep, clear as mud. sorry for that, not sure where my brain was then.

i know on some cars that the master cylinder is different depending on whether or not the vehicle was equipped with discs in the rear. however, i'm not sure what the differences were. i not sure if that was the case on the ZJ's. there were some that were offered with drums. this could be the cause of your rear locking early. one solution is that you could install an adjustable proportioning on the rear brakes to help prevent early lock up. have you tried locking up the brakes on a dry surface? it's possible that the wet surface you were on just magnified the early lock up.

if you want to do the WJ brake swap, there is a little more to it that just bolting on the calipers and rotors. you need the calipers, pads, rotors, and spindles from the WJ. you need wheel bearings from a 2000 XJ and wheel bearing spacers from JKS. if you want to use the WJ steering, you will either need new tie rods or modify the WJ setup. the XJ tie rods will work with the WJ spindles. i lost the links i had for doing the swap but if you google "WJ to XJ Brake Swap" you should be able to find a few pages. let me know if you have any other questions, i'll do my best to help.

zedpapa

 

here's a link.

http://www.4x4wire.com/jeep/tech/bra...kles/index.htm

zedpapa

 

it locks up on either dry or wet road on hard breaking
and thats for the link

 

I understood, (and agree with), your statement and was glad you posted it. Your later post was even more helpful as I don't have access to those links which are in my comp. in Tenn. (I'm in Mich. for awhile now). Thanks for posting them.