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Disc. Brakes Help !!!!!!

C

CMAHON

NAXJA Forum User
Location
Arlington, TX
I just converted to rear disc's on my 01 this weekend. I have read about others doing the ZJ swap with a good turn out. My issue is, that i see no improvment (maybe even worse) in stoping power. Anyone have the same result? What can i do to improve the stoping?
 
i did not change the prop. valve because every thread i read the poster said that it was not needed. Sorry I am new to brakes, what do you mean by bed routine
 
http://www.zeckhausen.com/bedding_in_brakes.htm

Also did you thoroughly clean the rotors before you installed them? I don't know if you used new or old rotors but new rotors come with oil on them. Did you thoroughly bleed them to?
 
I sprayed them down with brake cleaner (assuming the was enought). yes they are new also the pads and calipers. all of which i sprayed down. i bled them till no air bubbles and then went around again to be sure.
 
I'd have to bet on the proportioning valve or spring... swap that out and see if it gets better. Most threads I've seen indicate that you should swap that else your back brakes won't get enough pressure relative to the fronts.
 
The spring is actually inside the proportioning valve - it's what controls the balance of fluid sent to each set of wheels. Some people just swap the spring to avoid having to undo more brake line flare nuts. See http://www.go.jeep-xj.info/HowtoPvalve.htm for more information - hope this helps.
 
CMAHON said:
I sprayed them down with brake cleaner (assuming the was enought). yes they are new also the pads and calipers. all of which i sprayed down. i bled them till no air bubbles and then went around again to be sure.
Click to expand...

brakes should be bled from the farthest circuit to the closest (closest to the MC that is.)

do one rear, then the other, and back to the first (they share a line)
then do the pass front, and drivers front. you may have a bubble somewhere
 
tomcat said:
brakes should be bled from the farthest circuit to the closest (closest to the MC that is.)

do one rear, then the other, and back to the first (they share a line)
then do the pass front, and drivers front. you may have a bubble somewhere
Click to expand...
This is correct. The rear right has the longer line, it should be done first.

While you're under there inspect all your metal lines for rust and replace any bad lines you find - I didn't, and one of mine exploded the first time I panic braked, resulting in my sudden introduction to a guardrail and about a thousand dollars in materials and tools purchasing... at least I have an hvlp sprayer kit, a compressor, a good socket wrench set, and flare wrenches now...
 
Chances are the prop valve is your problem, however depending on what kind of brakes you put on, the calipers could be too big for the master cylinder. The pistons are bigger in a caliper than they are in a wheel cylinder on a drum setup. The master cylinder may not be able to move enough fluid to the rear to move the pistons far enough. If that is the case you will need a master cylinder sized right for your brakes.
 
alot of threads never get finished so i am re posting. i fixed my problem (error on my part). i had the calipers on the wrong side (bleader down, instead of up). fyi. i used 95 zj mounting plates. new 98 disc's, pads and calipers. the stoping power is the same as stock (i'm currently running 6in la and 35in mudders), maybe a little improvment, but nothing big. changing the valveing in the prop. valve will only improve the hard braking and i will do in the future but i think it is not needed now.
 
i did the crown vic swap and removed the o-ring in the prop valve(89 4.0 4in lift 31"bfg mudders on a danna44 rear) with positive results i am also planning on swapping in a wj99-04 brake boster and masterfor even better stopping power. with new pads and rotors they need time to mesh/break in together for proper stopping power.
 
Last edited:
Removing the o-ring is a bad idea. It effectively turns your front and rear brake systems into one. You lose pressure in one you loose all your brakes. Do it teh correct way by using a spring from a disc/dics ZJ.
 
CMAHON said:
the stopping power is the same as stock (i'm currently running 6in la and 35in mudders), maybe a little improvment, but nothing big. changing the valveing in the prop. valve will only improve the hard braking and i will do in the future but i think it is not needed now.
Click to expand...


 35"s put a lot of stress on the brakes.
I didn't notice a huge difference with the ZJ rear discs. The major advantages is not having the to worry about the adjusters freezing up or being too effected by water. They seem less prone to locking up when braking hard or on steep dirt downhills.
If you want to see a big increase in braking power, you need to upgrade the front discs to larger rotors and calipers such as the WJ or Vanco (Explorer) brakes.
 
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