Load Sensing Valve - Rear Wheel Brakes

[Chookman]

Just wondering what the adjustment proceedure is for the rear wheel brake load sensing valve is??
Is it necessary to adjust the valve after doing a spring lift given that there will now be a change in spring tension??

Thanks

Chook

[Ingenious-Eng]

Yes!!! you must adjust proportioning valve otherwise rear brakes will not work at full capacity making fronts do all the work, it is fitted to stop rear wheel lock up during hard braking when vehicle is empty, then when vehicle is loaded more braking pressure is allowed to the rear. Very scary to think just how many raised fourbies are out their fully loaded and no brakes.
Cheers

[Chookman]

Yes!!! you must adjust proportioning valve otherwise rear brakes will not work at full capacity making fronts do all the work, it is fitted to stop rear wheel lock up during hard braking when vehicle is empty, then when vehicle is loaded more braking pressure is allowed to the rear. Very scary to think just how many raised fourbies are out their fully loaded and no brakes.
Cheers

Do you know what the proceedure is to adjust the valve??
Have marked mine at original position and tweeked it a little but how far do I go??

Thanks

Chook

[bazzle]

Just lift the bracket with an extension on diff a few mm , ie 4" lift about 60mm on bracket seems to do the trick.

Bazzle

[Area54]

An extension bracket to raise the mounting point from the diff should be fitted. The spring needs to be level horizontally(neutral) - not an angle, and when the vehicle is parked level at static ride height, the spring needs to measure 207mm. Therefore when a load is applied to the cargo area, the spring will extend.

The valve itself is non rebuildable, and no adjustment is required of the valve.

[Heathx4]

This is GQ and on right? No such thing in an MQ? My rear brakes are now pretty slack compared to the fronts after replacing a lot of the crap in the rear drums (the leaking left rear axle seal also doesn't help). Used to be very much the other way around which was a bit scary!

[Area54]

I would assume that Chookman is talking GQ/GU (with no other info provided) I'm not sure of an MQ having the valve. it will be linked to your rear diff via spring or rod if you had one, only one way to find out...

Are your drum self adjusters in working order?

[Chookman]

I would assume that Chookman is talking GQ/GU (with no other info provided) I'm not sure of an MQ having the valve. it will be linked to your rear diff via spring or rod if you had one, only one way to find out...

Are your drum self adjusters in working order?

Ooops sorry.....yeah its an 89 LWB GQ discs all round.
If i'm understanding what your saying. With the ride height now approx 70mm above standard the spring is now under tension as if the car is heavily loaded.
If I now load the car, the spring will now return closer to horizontal (less spring tension) and will therefore reduce rear brake pressure.

The spring needs to be level horizontally(neutral) - not an angle, and when the vehicle is parked level at static ride height, the spring needs to measure 207mm.

Have measured my spring from end to end at 202mm. The valve end of the spring is also 25mm higher than the other.
Am slightly confused as to why my spring measures 5mm shorter than where it needs to be and is already under tension.

Any Ideas??
Thanks Heaps

Chook

[Area54]

I would assume that Chookman is talking GQ/GU (with no other info provided) I'm not sure of an MQ having the valve. it will be linked to your rear diff via spring or rod if you had one, only one way to find out...

Are your drum self adjusters in working order?

Ooops sorry.....yeah its an 89 LWB GQ discs all round.
If i'm understanding what your saying. With the ride height now approx 70mm above standard the spring is now under tension as if the car is heavily loaded.
If I now load the car, the spring will now return closer to horizontal (less spring tension) and will therefore reduce rear brake pressure.

The spring needs to be level horizontally(neutral) - not an angle, and when the vehicle is parked level at static ride height, the spring needs to measure 207mm.

Have measured my spring from end to end at 202mm. The valve end of the spring is also 25mm higher than the other.
Am slightly confused as to why my spring measures 5mm shorter than where it needs to be and is already under tension.

Any Ideas??
Thanks Heaps

Chook

Correct, the valve thinks you have a load on board, but the opposite happens when you do actually have a load on board, less rear braking pressure, because when vehicel is loaded the spring returns to the neutral phase.

At static ride height, vehicle unloaded the spring should be in the neutral tension position, so by extending the bracket this will brick the spring to the neutral position.

The panhard rod will be dragging your diff to the drivers side at static ride height, decreasing the length of the spring in your measurement. Quite possible that it may have been adjusted incorrectly in the past as well, prior to your ownership.

[Chookman]

The panhard rod will be dragging your diff to the drivers side at static ride height, decreasing the length of the spring in your measurement. Quite possible that it may have been adjusted incorrectly in the past as well, prior to your ownership.

Thanks Heaps

All making sense now.
Would you recommend a panhard rod up grade as well or isn't the lift significant enough to worry about it??

Chook

[Area54]

hard to tell without seeing/measuring the lift, but in most cases of moderate lift it's not necessary, unless the tyre is protruding outside the guard a lot, or you wheel the rig hard. The standard ones are thin wall tube, but it's not to say they are too weak for the average wheeler.

The legalities of altering the proportioning valve will vary from state to state, and best to check up with your RTA or an engineer. In QLD the procedure (for me) as follows: After setting up the extension bracket correctly, Nissan then checked the line pressures to ensure they were as per specification, in unloaded and loaded condition. Over the pits, the inspector wanted to see the paperwork from nissan - all fine, and I supplied details of the material, dimensions etc of my extension bracket. They could understand what I was trying to achieve, and the subsequent roller brake test confirmed all was well.

Ingenious-Eng is right - there must be thousands of rigs out there with this problem.

Just like every mod you do, it will create 10 other items to address.

Stay legal and safe.

[Chookman]

Ingenious-Eng is right - there must be thousands of rigs out there with this problem.

Just like every mod you do, it will create 10 other items to address.

Stay legal and safe.

I'm beginning to find that out.

Just recently had a four wheel alignment done and everything measures OK and all the wheels measure ok relative to the guards.

The proportioning valve spring is set at 202mm. Just had another look.
The way I see it at the moment is the valve screw will not allow the lever to travel outwards. If the spring was to now be released, the valve lever will stay where it is. The only way it will now pull in is for the suspension to travel upwards.

Was the 207mm a handbook spec or was that the end result of your line pressure testing.

Stay legal and safe.

Couldn't agree more. It WILL be changed.
Just getting my head around it all

Chook

[BowTieGQ]

I too was meaning to ask the question on adjustment after recently changing mine. I did notice that the valve appears to have its' own adjustment via the bolt. If you screw the bolt in or out this will give a unloaded starting point by determining the unsprung resting point of lever. Then you can adjust the lever on diff housing to determine the amount of proportioning in relation to the wheel travel. Is this correct and how do you set it? I think seat of pants is not quite good enough for brakes.

[Ingenious-Eng]

The valve itself is non rebuildable, and no adjustment is required of the valve.[/quote]

As Area54 explained DO NOT turn or adjust the screw/bolt on the hydraulic section of the valve only the actuation spring needs to be adjusted.
Cheers

[Chookman]

The valve itself is non rebuildable, and no adjustment is required of the valve.

As Area54 explained DO NOT turn or adjust the screw/bolt on the hydraulic section of the valve only the actuation spring needs to be adjusted.
Cheers

Yes!!! you must adjust proportioning valve otherwise rear brakes will not work at full capacity....

Took what you said initially in the literal sense without really understanding the mechanics of how it all works so was thinking the bolts needed adjusting.

So...I need to make a custom bracket that will set the spring at the right dimensions??
What is the adjusting screw used for ??

Sorry about all the questions brakes are too important to get wrong especially with the family on board.

Chook

[Ingenious-Eng]

The hydraulic adjustment bolt is used to set the valve up during manufactor of the part, the spring however is normally adjusted by a couple of slotted bolt holes on the bracket that attaches to the spring to the diff, however this adjustment doesn't allow for modifications to the suspension. So the idea is to position the bracket that holds the spring back to where it was when the vehicle was new by raising it, moveing it rearwards and also moving it sideways in relation to your new lift height. The reason for this is suspension movement isn't straight up and down, rather when you raise the suspension on either coil or leaf suspension the diff housing will rotate, move sideways and forward. This is why they fit different arms/panhards/shims etc. on the more extreme lifts, but technically all lifts should be adjusted, it's just out of the price range of most punters to be worried about it.
Cheers

[Chookman]

Thanks Heaps,

Info is very much appreciated.


Chook

[Area54]

Ingenious-Eng is right - there must be thousands of rigs out there with this problem.

Just like every mod you do, it will create 10 other items to address.

Stay legal and safe.

I'm beginning to find that out.

Just recently had a four wheel alignment done and everything measures OK and all the wheels measure ok relative to the guards.

The proportioning valve spring is set at 202mm. Just had another look.
The way I see it at the moment is the valve screw will not allow the lever to travel outwards. If the spring was to now be released, the valve lever will stay where it is. The only way it will now pull in is for the suspension to travel upwards.

Was the 207mm a handbook spec or was that the end result of your line pressure testing.

Stay legal and safe.

Couldn't agree more. It WILL be changed.
Just getting my head around it all

Chook

Yes that was the handbook spec. There is no need at all to touch any settings on the proportioning valve itself. I'll take a pic of the bracket extension and post it up for you.

This is not the sort of thing that - on the surface - DOT like to see (what looks like a backyard attempt at brake design corrections), however in my instance the inspecting officer was willing to pass it a) he could see the merit in what I was trying to achieve b) I had the correct supporting literature and research to back up my results. They also could not argue with the results from their own brake roller test...

[Chookman]

I'll take a pic of the bracket extension and post it up for you.

This is not the sort of thing that - on the surface - DOT like to see (what looks like a backyard attempt at brake design corrections), however in my instance the inspecting officer was willing to pass it a) he could see the merit in what I was trying to achieve b) I had the correct supporting literature and research to back up my results. They also could not argue with the results from their own brake roller test...

That would be great.
Was just thinking about material type.

Thanks Again

Chook

[Ingenious-Eng]

Just to clear up any confusion on valve operation, on the GU (I assume the GQ is set up the same) on a stock suspension vehicle, the valve allows full brake pressure to rear wheels during normal ride height and fully loaded ride heights, it only reduces brake pressure if you stand on the picks, the front end dives rear end raises that is the time the valve limits pressure to the rear to stop wheel lock up, so if you raise your vehicle and don't adjust valve your arse is up all the time (even when loaded) you will be on reduced brake pressure to rear wheels all of the time. The spring gets shorter when you raise the vehicle due to the panhard rod pulling the diff to the drivers side of the car, with a slack spring valve reduces pressure.

Please note most vehicle make & models (in particular utes) work completly opposite to this, you will still need to adust valve just keep in mind the valve doesn't work as described above. (Also some vehicle don't have a load sensing valve)
Cheers.

[legsx1]

Area 54 - re rear brakes
1/ Where is the 207mm measured from
2/ Have you posted some pics, if so where can I find them
3/ What is wrong with drilling some new holes in the bracket and moving it like that
4/ I too have lifted 2 inches in body and suspension and I am very interested in this subject, great comments
5/ Fitted a V8 and measured the vaccum at 20 inches where as the Nissan was 26 inches( I believe) comments please.

[china]

ditch the spring all together!! i did on my ute, works fine....

[Ingenious-Eng]

china, I'm keen to find out how you tested yours to work out it "WORKS FINE" which way did you set the valve, reduced or standard line pressure, do you carry or tow heavy loads or does this ute run around empty all the time? Also have you found any other things we can discard off of our Patrols???
D.O.T. Approved - You Betcha!!!

[china]

it was by accident i forgot to put it back on after do'n a coil convertion, bled the breaks and it all workn fine, yes it never has any wait in it, just for off road, maybe its all a coincidence??

[Ingenious-Eng]

China a ute running round empty as you've found out may be fine if the valve is sitting in the right spot or you dont jam on the picks to hard on a wet road, allso toss 750kg on the back and tow a 750kg trailer down hill and see if you can pull up O/K then! You need to find that spring, put it on and make a bracket out of 40 x 5mm steel flat to suit your lift, eg. for a 2" lift space hole centres 2" apart, bolt on both brackets and then adjust spring length as per manual. Now thats easier than bending over the pits with an D.O.T. inspector hanging out your arse isn't it?
Now D.O.T. much happier.

[china]

ok keep the spring.........
im no mechanic, still try'n to understand this, a stretched spring resembles no load, n a compressed with load, so no spring would imitate load ? oh me no understand.....
....it will find its way back one day ....

[Chookman]

Just to clear up any confusion on valve operation, on the GU (I assume the GQ is set up the same)..

Found this info in my GQ handbook.

"The load sensing valve is a device incorporated into the brake system that senses the amount of weight (passengers, equipment, etc.) on the rear of the vehicle and increases the rear brake fluid pressure to compensate for additional load....

In the event of poor breaking performance have the system adjusted by a dealer service department. Poor breaking performance could meanthat the rear wheels lock when braking with little weight in the rear or they do not provide enough braking when the rear is carrying a load."

Interestingly enough that is the only referal for any adjustment that should be made by a dealer. Engine rebuilds and even other parts of the braking system do not carry this recommendation which suggests to me its pretty important.

The handbook I have (not a Nissan workshop manual) offers no suggestion on how to adjust the valve at all.

Chook

[Josh_GQ]

Also have you found any other things we can discard off of our Patrols???
D.O.T. Approved - You Betcha!!!

get rid of those sway bars, just excess weight

[Ingenious-Eng]

Interestingly enough that is the only referal for any adjustment that should be made by a dealer. Engine rebuilds and even other parts of the braking system do not carry this recommendation which suggests to me its pretty important.[/quote]

Yes Chooky your right, it's very important!!!

As for removing swaybars, I did on the front of my Navara, notified insurer about all mods was told in no uncertain terms put sway bar back on or no insurance. So it on but still gots good articulation - very simple & sneaky mod!!!
Cheers.

[Area54]

Area 54 - re rear brakes
1/ Where is the 207mm measured from
2/ Have you posted some pics, if so where can I find them
3/ What is wrong with drilling some new holes in the bracket and moving it like that
4/ I too have lifted 2 inches in body and suspension and I am very interested in this subject, great comments
5/ Fitted a V8 and measured the vaccum at 20 inches where as the Nissan was 26 inches( I believe) comments please.

the 207mm is the length of the spring - contact point on the inside of the hook on each end of the spring.

Pics follow.

You have to extend the spring mount vertically not laterally, so extra holes won't help in this instance.

Vacuum, how heavy do you find the brakes?