How to properly adjust a brake system proportioning valve

[JONNYFJ]

Does anybody know how to do this properly I have had backyard mechanics tell me, but have never noticed a difference. Also where should the valve be mounted. I was told towards the rear near the rear brakes, is this true?

[JONNYFJ]

Seriously no one knows?????

[bikersmurf]

The location shouldn't matter. Stock landcruiser is on a bracket under the master cylinder. Toyota pickups are often mounted on the frame above the rear axle.

I adjusted mine by braking on varying surfaces until the rear brakes were not locking up all the time.
I kept adjusting it until felt right. I then confirmed it by having a local brake shop run it across there skid pad.

[JONNYFJ]

I see. So what your saying is bring it to Break Check

[bikersmurf]

I was able to adjust it properly by trial and error (Four wheel disc brakes). The brake test performed on the skid pad showed the balance front to rear and also the balance side to side. If you don't have it close the brake shop may want to charge you for there assistance.

[DSRTRDR]

I mounted the valve by the master cylinder

to adjust it, we took the truck on a dirt road and I stepped on the brakes hard while going 15-20 mph, while my husband watched front/rear lock up

then adjusted the valve so that the front would lock before the rear

repeated several times and tested on flat as well as downhill several times again

[dgangle]

I went to an office park on the weekend when there were no cars. The asphalt had just been resealed...you know the type of place...very black, stinky and very slippery especially when wet. Moving around to different spots I'd do some aggressive stops while adjusting the front to rear brake bias with the adjustable proporting valve. It left nice, black, long marks from each tire. They probably didn't appreciate it come Monday but whatever. 33's make a heck of a howl that freaks some people out.

I go through this drill when I add/remove my hartop as the extra weight changes the bias needed. I like the fronts to lock up just before the rears. Vice versa and you have your hands full on a short wheel-based vehicle.

I have mine under the hood. The circle track guys mount them so the driver can adjust during the race as traction/track conditions change. Now that would be the shitz.

[bikersmurf]

If your front brakes are locking up you're loosing the ability to steer. With disc brakes on the front they should be almost impossible to lock up. If you're jumping on the brakes that hard the rears should also be locking up. I prefer to have all of the brakes lock up at the same time on loose surfaces. On dry pavement that'll mean the fronts will never lock up and the rears will lock when the back comes off the ground. You'd be surprised how fast my 4700 lb FJ40 will stop.

Be aware that if the rear is locking up too fast it will want to pass the front in sudden stops (spin out).... which I wouldn't want. But having the fronts lock first will prevent you from avoiding the kid that just ran out on front of you.

If you take it from one extreme to the other and then back and forth you should be able to tweak it so your rig will stop on a dime. Faster than the camaro now parked under your rear bumper.

[JONNYFJ]

My 40 barely stops on a city block let alone a dime haha. I am going to take it to a brake mechanic. Last TLCA meeting I was driving home and the light turned red but I was just along for the ride because the 40 was not stopping

[bikersmurf]

It sounds likes your breaks are out of adjustment... or you've got bigger problems than just Porp valve adjustment. I'd get it checked out before something bad happens.

[Downey]

Any brake shop can adjust your front-to-read proportioning with gauges, should be in the 60% front to 40% rear ball park.

[dgangle]

Stainless Steel Brakes sells kits for this purpose. I paid $50 a few years back and it is a very valuable tool for the $$.

Jim, I know this has been discussed B4 but what kind of pressures should one expect for front disc/rear drum and front & rear discs??? It may good to note it here in this thread.

[Batalia]

I don't think my cruiser has a proportioning valve. Sometimes my rear left tire locks up if I brake to hard. Where can i install one so i can place more pressure on the front bakes then on the back?

[dgangle]

Originally Posted by Batalia

I don't think my cruiser has a proportioning valve. Sometimes my rear left tire locks up if I brake to hard. Where can i install one so i can place more pressure on the front bakes then on the back?

-----thread hijack-------

If you have one rear that is locking up a proportioning valve prolly isn't going to help. You got other issues to look into that could be anything from a simple adjustment to a seized wheel cylinder, worn shoes, broke/missing return spring, contamination of the shoes, etc. Take them apart and see what's going on.

A proportioning valve (non-adjustable like the OE or adjustable like those offered from Willwood, Summit, etc) is nothing more than a regulator. It goes in the rear circuit and is used to take a pressure drop on that line's pressure, thus reducing the braking force.

If you want some help determining if you have/need one we are going to need more info and pictures never hurt.