Disc. Brakes Help !!!!!!

Removing the spring puts more pressure to the rears instead of proportioning it down. Many guys add 4 wheel disc, don't get great results, remove the spring and now have better brakes. Same would have happened if they just removed the spring and left the drums on.

For you guys removing the spring, go 35 MPH and lock up your brakes. If you stop straight fine, if your ass end comes out think about what will happen at 70 MPH (roll, crash, burn, crispy human flesh).

There's a reason it's called a proportioning valve and it is needed. You guys are removing the proportioning part out of that valve. It will only matter if your capable of locking up the brakes, but if you can and the rears lock up first, bad things happen.

Vancopbs said:

Removing the spring puts more pressure to the rears instead of proportioning it down. Many guys add 4 wheel disc, don't get great results, remove the spring and now have better brakes. Same would have happened if they just removed the spring and left the drums on.

For you guys removing the spring, go 35 MPH and lock up your brakes. If you stop straight fine, if your ass end comes out think about what will happen at 70 MPH (roll, crash, burn, crispy human flesh).

There's a reason it's called a proportioning valve and it is needed. You guys are removing the proportioning part out of that valve. It will only matter if your capable of locking up the brakes, but if you can and the rears lock up first, bad things happen.

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WHy not just run the correct prop valve to accommodate the 4 wheel disc swap?

There's actually almost zero difference in prop valves from 1990-2006 jeep 2 or 4 wheel disc valves.

i have had no issues with my zj conversion and i did not change the pv. i did not notice much of a difference. i think there is one but minor.

my big thing was to keep from having one of my back tires lock up randomly while im in a turn when its wet. i hate drums and i like the smooth even braking i get no matter the conditions. that and the ease of changing pads.

i have been meaning to test a quick stop to see if the rear steps out or not. i don't think it will thou.


what did you do for the parking brake?

RedChuck said:

what did you do for the parking brake?

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I chopped the ends off the ZJ parking brake levers and did the same to the XJ drum parking brake levers. The XJ ends were then welded onto the ZJ's lever, allowing the use of the stock XJ parking brake cables.
The parking brake bracket needs to be moved rearward to provide the extra length needed for lifted XJs.
http://www.madxj.com/
Look under 'Technical' for 'Parking Brake Bracket Relocation'
At 4" of lift, the cables have enough slack to keep from binding when flexed.[/FONT]

I found my braking performance to get better with time, as the components seasoned or bedded in or whatever.
Also - consider the pads. Did you go cheapo? I did, because I'm poor - but to go from OEM drums in good condition to cheapass rear disc isn't going to yield the best results.

I found my braking performance to get better with time, as the components seasoned or bedded in or whatever.
Also - consider the pads. Did you go cheapo? I did, because I'm poor - but to go from OEM drums in good condition to cheapass rear disc isn't going to yield the best results.

CMAHON said:

...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.

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A lot has been written about prop valves and that they only work under hard braking, etc. When I did my rear disk swap I had basically no improvement in braking after the disk brake swop while retaining the stock prop valve. However, when I changed it to a ZJ prop valve (only swopped over the plunger and spring) there was a day and night difference. I would strongly recommend you do the prop valve swop. A quick check on how effective your rear brakes are (and whether the proportioning is correct) is the lift the rear end of the Jeep, start the engine and put it in gear for the rear wheels to spin. Apply the brakes and see how easily and effectively your rear wheel stop turning when applying moderate braking power. I bet with the stock prop valve the rear wheels might even still be turning when applying moderate pressure on the brake...

Talyn said:

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.

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When I swapped my prop valve internals from the ZJ one to my XJ's prop valve I tried to verify the accuracy of this statement by looking into the prop valve and see how the front/rear systems are separated. Removing the O-ring does nothing for the front/rear separation as the two systems are separated by a sliding switch which will only move when there is large drop in pressure of the one channel compared to the other. All the the o-ring does is to effectively remove rear brake proportioning and thus give 50-50 braking front and rear. The front/rear channel separation and thus that safety feature remains.

I just have to ask................. Are your bleeders on TOP of the caliper or on the bottom???? If they are on the bottom you have them installed incorrectly! left vs. right! Your bleeders NEED to be on TOP!!

Adding to this old thread in case anyone uses the search feature- I removed the stock proportioning valve and added an adjustable on my rig with the Crown rear disc brake conversion. That being said, its left on wide open and I cannot get all 4 to lock up in the dry, and the fronts lock first in the wet. I will be removing the proportioning valve to use it in a vehicle that actually needs it.

chpmnsws6 said:

Adding to this old thread in case anyone uses the search feature- I removed the stock proportioning valve and added an adjustable on my rig with the Crown rear disc brake conversion. That being said, its left on wide open and I cannot get all 4 to lock up in the dry, and the fronts lock first in the wet. I will be removing the proportioning valve to use it in a vehicle that actually needs it.

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Were you able to lock up all four wheels before installing the adjustable proportioning valve?
Brake systems should always be setup to lock the front brakes before the rears. This prevents spinouts and is the reason why proportioning valve are installed in the first place.
The adjustable valve should not change the performance of the front brakes unless there is a leak or air in the system.
Let us know how it works out.