Load Sensing Valve

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25 Apr 2015 13:52 #2 by DarrenWebster303
DarrenWebster303 replied the topic: Load Sensing Valve
Paul, East coast Okas has them. 0418125428

In the post same day Pete.

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25 Apr 2015 15:47 - 25 Apr 2015 15:48 #3 by dandjcr
dandjcr replied the topic: Load Sensing Valve
Peter, this older thread contains some useful info.

Also a search for "load sensing valve" will throw up a few others.

David

David and Janet Ribbans - Oka 148
Oka148 profile here.
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Last Edit: 25 Apr 2015 15:48 by dandjcr.

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25 Apr 2015 18:24 #4 by Outback Jack
Outback Jack replied the topic: Load Sensing Valve
Ford and late model Commodore utes have them.

Go down to your local wrecker and get one of a VY/VU ute or similar.

They will 10mm fittings for memory with OKA being imperial.

I cut the old fittings off and reflanged new metric fittings for memory..........


I brought a brand new valve for around 250 for memory.

If you find an old one a rebuild kit cost not much at all.

Other option is to contact Paul, this would be the easist option if you dont want to get one from an wrecker.

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26 Apr 2015 06:33 #5 by Paul Scherek
Paul Scherek replied the topic: Load Sensing Valve
I have often wondered about that brake proportioning valve. My springs are a bit non-standard and it sits quite high despite its travel weight of nearly five tons. The brakes seem to work perfectly, and I have never had the back step out However, when doing a long stretch of winding downhill road, the rear brakes get much, much hotter than the front brakes. Is this normal?

Cheers,
Paul

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26 Apr 2015 09:03 #6 by Peter_n_Margaret
Peter_n_Margaret replied the topic: Load Sensing Valve
As part of our recent GVM upgrade, we did brake tests on an airfield.
Initially, the rear brakes were locking prematurely. We reduced this tendency by adjusting the proportioning valve.

Cheers, Peter.
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Mob.0428171214

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26 Apr 2015 12:15 #7 by Paul Scherek
Paul Scherek replied the topic: Load Sensing Valve
Thanks Peter, I might try to find a good bit of dirt to try that on - I figure we are more likely to get into trouble on dirt with locking back wheels than we are on bitumen with slightly less effective rear brakes, if that makes sense. (If I set the rears up for dirt, they presumably would be less than ideally sensitive on bitumen).

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25 Jun 2017 21:41 #8 by Frank
Frank replied the topic: Load Sensing Valve
resurrecting this thread, rather than creating a new one.

I pulled the load sense valve off 135 as it was seized solid. Pulled it apart and then tried to get a rubber kit for it. Doesn't exist.
So following the recommendation of this thread I asked about one for a Commodore Ute. Was told they can do an exchange, but the fellow said that the Commodore one doesn't have the same internals as the Oka unit I showed him.

So I bought a Commodore unit (VR model ute) and pulled it apart. He was correct. Quite different.

Internal piston/valve (commodore top)
Internal assembly (commodore top)

Internal valve unit (commodore left)

Note the little one way valve internal to the Commodore unit.

Do they work the same? I don't know yet, hoping to be able to rig up a hydraulic test kit with a couple of pressure gauges and find out.

Almost no part of the Commodore unit is interchangeable with the Oka, Internals of housing are different, external spring, load arm springs, all different. It just looks the same at first glance.


Rang Oka Parts, Dean said he has removed the valve on his Oka and replaced it with a straight joiner.
So rear discs will get the same pressure as front discs.
I think for a camper situation where the vehicle is always heavily loaded this is the way to go, and this is probably what I will do with 164 (I assume it is also rusted solid).
However, after doing this I would think some testing on a gravel road would be in order.
Also for a single or dual cab (135), I have some reluctance in proposing this. Thankfully the seals in the Oka unit actually look OK. Unlike the Commodore one that was leaking!
I have rung Paul, but he hasn't rang me back yet. So no idea what his advice is.

Frank & Christine Thomas

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25 Jun 2017 22:54 - 25 Jun 2017 23:17 #9 by dandjcr
dandjcr replied the topic: Load Sensing Valve
Frank, the Commodore Ute valve is the only one I can find after a search, which looks remotely like the Oka one.



There's a new one available on Ebay from here for $80 (+$15PP), second listing, didn't sell first time, need to bid, used ones are around $130-180.

Vehicles and pressures may be different but the proportioning principle is the same so worth a try if you can't get a repair kit??

David

David and Janet Ribbans - Oka 148
Oka148 profile here.
Visit our technical and travel blogs: here.
Last Edit: 25 Jun 2017 23:17 by dandjcr.

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26 Jun 2017 09:44 #10 by John and Bronwyn
John and Bronwyn replied the topic: Load Sensing Valve
"but the proportioning principle is the same"

The principle may be the same but there is probably devil in the detail.

This is from stoptech.com/technical-support/technical...proportioning-valves
I can think of 3 parameters (there are probably more) which could be different - the threshold where the limiting action starts, the "proportionality" factor between front & rear brake pressure after it starts, and the relationship between vehicle height and change in the limiting action threshold.
Doesn't help, I know!
However if you are going to set it up on a test bench, it should be possible to find out these various factors for the old valve and then be able to replicate them in an adjustable valve.
Where to get an adjustable valve? Dunno, but the article referenced above talks about them, so presumably they are available somewhere......

Good luck!
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26 Jun 2017 21:04 - 27 Jun 2017 04:31 #11 by Holmz
Holmz replied the topic: Load Sensing Valve

Paul Scherek wrote: Thanks Peter, I might try to find a good bit of dirt to try that on - I figure we are more likely to get into trouble on dirt with locking back wheels than we are on bitumen with slightly less effective rear brakes, if that makes sense. (If I set the rears up for dirt, they presumably would be less than ideally sensitive on bitumen).


Imagine a 4m wheelbase and the centre of mass 1 M off the ground...
...and that there are 2 tons on both the front and the rear axels.

Now tie some lead weights on a string and hang them of f the centre of mass.

the weight will hang straight down, until one hit the brakes. On dirt maybe one gets 0.5G, so the weight will hang forward at ~30 degrees.
And the front axel force will be on the order to 2.5 tones and the rear 1.5 tones.

Now do the same on bitumin and get 1G of braking.
The string will hand forward at 45 degrees and the front axel force will be 3 tones and the rear 1 ton.

So you will need a proportioning valve more on bitumin than on dirt, if it all goes pear shaped.

On ice or snow one does not even need the proportioning valve.

[edit]
Where does the valve sit?
Has anyone used something like: www.summitracing.com/int/parts/ssb-a0707-1/overview/ ?
They are less in vogue in these days of ABS... but the traditional solution if one does not want a balance bar and one cannot lower the vehicle enough.
Last Edit: 27 Jun 2017 04:31 by Holmz.

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27 Jun 2017 05:25 #12 by Paul Scherek
Paul Scherek replied the topic: Load Sensing Valve
Very interesting point, Holmz, and makes good sense.
On top of that, under heavy braking the front dips and the rear rises thus reducing the amount of braking on the rear axle. There are lots of dynamics in play for such a superficially simple device as the proportioning valve.

The valve on 041 seems to be stuck - the back wheels lock on bitumen very easily. On 059 (with the motorhome body) the back brakes seem to do very little - as I discovered when a front brake hose blew out.

Where does one find an Oka-competent brake specialist?

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27 Jun 2017 05:30 #13 by Paul Scherek
Paul Scherek replied the topic: Load Sensing Valve
I like the looks of that Summit valve. 059 has a pretty constant weight so although this valve wouldn't take into account the rising of the back axle under heavy braking, I am sure it would be better than the non-working valve currently fitted.

Can anyone tell me please the thread type of the original proportio0ning valve? The Summit is 1/8 NPT.

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27 Jun 2017 06:38 - 27 Jun 2017 06:40 #14 by Lang
Lang replied the topic: Load Sensing Valve
On our very first trip in #200 (to the Grafton gathering) I found the front brakes locking on the gravel at very slow speed going along the steep entrance road. Result was total loss of steering.

After getting home I adjusted the load sensing valve height position. This completely solved the problem and have never since had the brakes lock, front or rear, independently on any surface or terrain.

I recently went over a weigh bridge fully loaded and weight front and rear is within 100kg.

Lang
Last Edit: 27 Jun 2017 06:40 by Lang.

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27 Jun 2017 16:59 #15 by Dean and Kaye Howells
Dean and Kaye Howells replied the topic: Load Sensing Valve

Frank wrote: I have rung Paul, but he hasn't rang me back yet. So no idea what his advice is.


I spoke to Paul today about the proportioning valve assembly. There's no rebuild kit that he is aware of but he can provide a replacement assembly (non Oka) with line adapters to suit the Oka fittings.

Deano :)

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27 Jun 2017 20:47 #16 by Outback Jack
Outback Jack replied the topic: Load Sensing Valve
There was a place in Adelaide who had reseal kits.

I used a late model Holden commodore one. I think for memory it has 10mm fittings. I just brought the new fittings

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28 Jun 2017 06:32 - 28 Jun 2017 06:36 #17 by dandjcr
dandjcr replied the topic: Load Sensing Valve
You could try Power Brakes SA on North East Road, Adelaide, (08) 8261 0888 or This email address is being protected from spambots. You need JavaScript enabled to view it.. Mail order service too.

They surprised me by having Bendix brake parts (pistons/seals) in stock for my Oka brakes but also stock/repair proportioning valves.

David

David and Janet Ribbans - Oka 148
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Visit our technical and travel blogs: here.
Last Edit: 28 Jun 2017 06:36 by dandjcr.

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28 Jun 2017 17:55 #18 by Frank
Frank replied the topic: Load Sensing Valve

Paul Scherek wrote: Can anyone tell me please the thread type of the original proportio0ning valve? The Summit is 1/8 NPT.


7/16"-24tpi inlet and outlet 1/4" pipe

Frank & Christine Thomas
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22 Sep 2019 01:35 #19 by Rick Whitworth
Rick Whitworth replied the topic: Load Sensing Valve
Does anyone have any suggestions on an effective method for getting the tension on the brake proportioning valve right?

After 100,000 kms I am now due for my 3rd set of pads on the rear but front pads are still original ones and are still not too bad.
You would think it should be the other way round.
Truck stops OK but do need to take usual care mountain driving.

Dont want to adjust then wait until next set wears out to see result.
Has anyone tried some sort of drive test - adjust cycle that works?

Rick Whitworth: OKA XT 149.

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22 Sep 2019 10:19 - 22 Sep 2019 10:21 #20 by Lang
Lang replied the topic: Load Sensing Valve
Rick

If you look back on the thread you will see Peter did a practical test on an airfield by actually seeing if front or rear locked on loose surfaces.

This really is the only way to go because all the theory and measurements in the world will never get it right. Each vehicle has different weight distribution, tyres, brake efficiency/linings, and suspension components/height.

An hour on a loose surface (you could do it on sealed but the black marks and tyre wear might be unacceptable) would see you with all four wheels locking at the same time with heavy braking and a nicely balanced braking system tailored for your particular vehicle.

Lang
Last Edit: 22 Sep 2019 10:21 by Lang.
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22 Sep 2019 11:00 #21 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: Load Sensing Valve
Rick the actual valve is from an early Holden 1 tonner same as
I have a friend with one and I'll ask him if he has a manual and if it covers adjusting the valve.
I have done similar to Lang suggested to adjust it and then try on a loose dirt road to see where it locks up.
A couple of years ago the local servo stopped doing annual heavy vehicle rego inspections and I had to take the Oka to a truck place and they put it on a rolling road to test the brakes, first try the rear on the Oka couldn't even slow the rollers down, I hopped under and let the proportioning valve arm go and sit up against the floor, the brakes worked well then! Since then I've fiddled around with the adjustment after resetting the rear springs and it is now braking pretty evenly.
I've found that if the Oka starts to suffer from squeaky brakes under light brake application then it is a sign that the rears aren't braking as hard as they should.

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 680w solar, diesel cooking heating and HWS,
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