My Brakes are spongy and dont stop for shit. do i need a proportioning valve? do i put it on the front or rear brakes? please help

Hardcore tech would be building your own prop valve, providing pictures and design documents, and telling us which circuit to install it in :shaking:

what kind of rig is it? does it already have a satock prop valve on it? so u put 4 wheel disc on it or did it already come with 4 wheel disc? please more info is needed for a good answer.

87 yj with d44 front and a sf 14 bolt rear. yes i put it on myself, and it has the stock prop valve. dont know if it can be reset or not.

Remove the square o-ring from the stock prop valve. It will greatly improve rear braking ability.

Where is the o-ring located?

What size master cylinder is on it? What size calipers are you running on the rear and front. Proportioning valves do not affect "spongy" pedals nearly as much as too small of a master cylinder. My guess is you are running around a 1" master with a 6:1 ratio using 2 7/8 calipers front and rear.

Most 4 wheel disc masters are anywhere from 1 1/16-1 1/4" bore. This is also why most choose to run the smaller 2 3/8 bore (S10, Monte Carlo) caliper in the rear as you don't have such an equal amount of force on each rotor.

To cover the other part: your stock proportioning valve actually has a circuit in it that activates the rear brakes first to allow the drums time to expand before the discs engage. There was some tech around here about taking it apart but I don't feel like searching for it. I just took the stock valve out and ran a Wilwood adjustable one on the rear

there are a chit load of posts on this exact issue & no need to reinvent the wheel here again. do a little searching and you'll find the info your looking for.

76 d44 calipers with the stock master cylinder.

There is a nut on the end of the prop valve. Unscrew it, you will find a square o-ring inside. Remove the o-ring, bleed system and you will have better brakes. That o-ring reduces pressure to the rear brakes.

Bleed the damn brakes properly, and they won't be spongy (unless your master cylinder is fawked.)
Most times someone has problems with a spongy pedal w/ a disc conversion, it's because they mounted up the calipers w/o the bleed valves being at the exact top. If they're not exactly on the top of the caliper bore, no matter how many times you bleed 'em, they're going to have an air bubble left inside.
Air compresses. Fluid does not. The air in the system is what causes the spongy pedal.
If the bleed valves aren't at the top, either lift one or the other of the vehicle until they are at the top, then bleed, or... if that won't get them at the top, undo one of the mounting bolts on each caliper, swing the calipers up until the valves are at the top, slip a piece of wood (the thickness of the rotor or greater) between the pads to keep 'em spread apart (and to prevent your pistons from popping out) and bleed 'em 'til they run clear.

...and the part that most people mistakenly refer to as a proportioning valve is actually a combination valve. It contains a proportioning valve, but has two other functions, as well. Do a google search and read up on what it does.
Simply slapping an adjustable proportioning valve in the system, in place of the stock combo valve, is not really taking care of things...

Remove the square o-ring from the stock prop valve. It will greatly improve rear braking ability.

There is a nut on the end of the prop valve. Unscrew it, you will find a square o-ring inside. Remove the o-ring, bleed system and you will have better brakes. That o-ring reduces pressure to the rear brakes.


I tried that and it helped a little, but still felt a little spongy. Bypassing the valve all togheter helped TREMENDOUSLY!

I'm running Ford D60 (dual piston calipers) and a 14FF rear with '75 C20 disk brakes. That's with running 4:1 t-case and 5.13s.

It stops better then when I was with stock axles and 35s. It wouldn't stop for shit then. Coming down off rocks was a bitch. :emb3:




p.s. I am also running the "E350 master cylinder."

I ran the stock master with 0-ring removed on GM front 60 calipers and half ton rear calipers. I agree it was better but not how I like it. I then went with a 79 Bronco master. I could lock all for at speed with a good push of the pedal.



I tried that and it helped a little, but still felt a little spongy. Bypassing the valve all togheter helped TREMENDOUSLY!

I'm running Ford D60 (dual piston calipers) and a 14FF rear with '75 C20 disk brakes. That's with running 4:1 t-case and 5.13s.

It stops better then when I was with stock axles and 35s. It wouldn't stop for shit then. Coming down off rocks was a bitch. :emb3:




p.s. I am also running the "E350 master cylinder."

texas blake: did you also run another prop valve?

texas blake: did you also run another prop valve?

No. It was easier just to remove it.