Load Sensing Valve

  • Peter and Sandra OKA 374
  • Peter and Sandra OKA 374's Avatar
  • Away
More
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,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.
The following user(s) said Thank You: Rick Whitworth

Please Log in or Create an account to join the conversation.

More
22 Sep 2019 12:03 #22 by Peter_n_Margaret
Peter_n_Margaret replied the topic: Load Sensing Valve
My brake tests were actually done on a sealed runway, but in any case, you DO NOT want the rears to lock without the fronts because the consequence is that the vehicle is likely to swap ends and in trying to do that is likely to fall over.
Cheers,
Peter

Cheers, Peter.
OKA196 tinyurl.com/OKA196xtMotorhome
Mob.0428171214
The following user(s) said Thank You: Rick Whitworth

Please Log in or Create an account to join the conversation.

  • Peter and Sandra OKA 374
  • Peter and Sandra OKA 374's Avatar
  • Away
More
22 Sep 2019 12:23 #23 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: Load Sensing Valve
The later model holden VT VS utes had a similar unit to the one tonners but it has a different mounting bracket but parts might be interchangeable.

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 680w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.
The following user(s) said Thank You: Rick Whitworth

Please Log in or Create an account to join the conversation.

More
22 Sep 2019 15:51 #24 by mort
mort replied the topic: Load Sensing Valve
Hi Rick,
Well that is a good question.
The balance between front and rear is usually 60% front 40% rear or there abouts depending on vehicle.
There are a few ways to do this.
1 take it to a brake place that has rollers and set up for it usually truck service centers.
2 get a set of manual ajusters which the driver can set while driving like race cars.( too much trouble )
3 do it yourself ajust drive brake ajust drive brake untill you are happy the only thing is you wont know what the % is between front and rear.
At the moment you have the rear doing most of the braking which in an emergency braking its not good.
Martyn
The following user(s) said Thank You: Rick Whitworth

Please Log in or Create an account to join the conversation.

More
17 Nov 2019 16:25 #25 by Peter Davis
Peter Davis replied the topic: Load Sensing Valve
Hi Rick
Did you work out why your front brakes aren't working as hard as the rear?
Mine does the same. The rear brakes get very hot and the front warm.
In the process of changing front calipers. Hopefully that will help. Except I broke the retaining bolt which holds the slider spring arrangement holding the caliper in place.

Please Log in or Create an account to join the conversation.

  • Peter and Sandra OKA 374
  • Peter and Sandra OKA 374's Avatar
  • Away
More
17 Nov 2019 16:46 #26 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: Load Sensing Valve
Peter you can adjust the proportioning valve, there is a bolt and locknut which gives fine adjustment and the coarse adjustment is either/and the sliding section of the arm or shortening/lengthening the cable/chain between the diff housing and the end of the arm.
A crude and simple fix is to bend the bracket on the diff up to increase braking on the rear or down to decrease braking on the rear. To put it simply the arm needs to go up to increase braking force on the rear and down to decrease braking force.
Up here in NSW heavy vehicles need an annual inspection for rego and last year after resetting the springs I discovered on the brake testing rollers that the rears were doing virtually nothing. A quick removal of the cable between the diff and the proportioning valve arm saw the rears back to full braking for rego purposes and then when I got home I spent a bit of time on a dirt road adjusting the length of the cable/bending the bracket and adjusting the adjustment bolt to get it right.
The dirt/loose surface allows you to easily lock the rears when you jump on the brakes so as to easily adjust the rears to get them braking correctly.

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 680w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.
The following user(s) said Thank You: OKAPETE

Please Log in or Create an account to join the conversation.

More
17 Nov 2019 18:56 #27 by Peter Davis
Peter Davis replied the topic: Load Sensing Valve
Does the brake proportioning valve just decrease the amount of braking to the rear brakes. Or does it effect the front brakes as well. So if it was allowing full flow to rears wouldn't that be the same braking force as the front.

Please Log in or Create an account to join the conversation.

More
18 Nov 2019 00:13 - 18 Nov 2019 00:18 #28 by Rick Whitworth
Rick Whitworth replied the topic: Load Sensing Valve
Gday Peter
I replaced the rear pads but then got caught up with major house reno so have not gone further with setting up sensor valve yet.
My truck stops well. Just trying to even up wear rates front and back.
Have had a couple panic stops where I had to throw out all anchors. One with the boat on the back crossing the Swan St Bridge when a bike did a u turn from left without looking. I locked up all 4 oka wheels plus trailer brakes in huge cloud of smoke and left rubber on the bitumen from all tyres.
It was nice to find it stops that well but not something you would do on purpose, even in a test.
On each occasion the wheels were straight, otherwise I am sure I would have turned it over.
I did a brief search for a City service center with front and rear rollers who might be able to test it but no joy. If there is one I bet they charge, bit like the suspension shaker places
Local center that sold me the pads said I should just monitor the difference in the front rear pad thicknesses but there may not be direct relationship between equal wear and good braking performance anyway. Maybe when sensor is well balanced for bitumen on a motorhome setup, rears do wear quicker.
So when I get time I plan to do some adjusting and drive testing as suggested above.

re your question I figure the sensor must affect both the front and rear, it is a proportioning valve, so for a given peddle pressure modifying the sensor lever to decrease pressure to one end, increases pressure to the other end.
This is supported by owners who say if it is set too tight (ie low lever) all pressue goes to the front causing dangerous lockup effecting steering.
It will be a while before I get back to my adjustments/tests but will report back if I have any success

Rick Whitworth: OKA XT 149.
Last Edit: 18 Nov 2019 00:18 by Rick Whitworth.

Please Log in or Create an account to join the conversation.

  • Peter and Sandra OKA 374
  • Peter and Sandra OKA 374's Avatar
  • Away
More
18 Nov 2019 03:20 #29 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: Load Sensing Valve
Looking at the plumbing I don't think it affects the front at all, the same unit on a Holden 1 tonner certainly doesn't, if it did then ALL the brake lines for both front and rear would have to go through the valve and only the rear ones do.
There is probably some very small effect on pedal pressure due to fluid being forced through a smaller aperture but it would be negligible.
Peter you want less braking on the rears the less weight is on the back, in mine and Ricks case and probably yours where we have a lot of weight in the back with a motorhome fitout the weight is pretty well balanced, even with a 6bt and Allison mine is within 100kgs front and rear normally but goes rear heavier when fully loaded with fuel and water for a long trip.
But the problem is that the weight doesn't stay in that exact relationship during braking as the weight "shifts" forward under braking as the front of the truck drops and rear lifts, the harder you brake the more it occurs.
So if you have the rears braking as much as the fronts then the rears will lock especially under hard or emergency stops. Hence the need to adjust the valve to suit the particular vehicle. Once it is setup for your particular situation then it shouldn't need any more adjustment unless you remove a lot of weight.

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 680w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.

Please Log in or Create an account to join the conversation.

More
18 Nov 2019 06:27 #30 by Rick Whitworth
Rick Whitworth replied the topic: Load Sensing Valve
You are right re plumbing Peter.
My use of words "for a given peddle presure" was wrong.
In practise what happens is the driver is looking for a certain amount of braking so that if the sensor lever has been set to give inadequate pressure on the rear the driver automaically compensates with heaver foot to get the required deceleration.
So the effect is that front pressure goes up to compensate.

Rick Whitworth: OKA XT 149.

Please Log in or Create an account to join the conversation.

  • Peter and Sandra OKA 374
  • Peter and Sandra OKA 374's Avatar
  • Away
More
18 Nov 2019 06:44 #31 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: Load Sensing Valve
Yes it is amazing how you compensate, when I did the springs which effectively raised the Oka about 40mm at the front and 60 at the rear I didn't really notice the decreased braking from the rear until it failed to even slow the rollers on the brake test machine. I had just pushed harder on the pedal !

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 680w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.

Please Log in or Create an account to join the conversation.

More
18 Nov 2019 07:53 - 18 Nov 2019 07:58 #32 by Dean and Kaye Howells
Dean and Kaye Howells replied the topic: Load Sensing Valve
My understanding of the load proportioning valve is that it varies the braking effort to the rear wheels depending on the load carried by the vehicle. The more the vehicle is loaded the more the rear springs sag which causes the arm attached to the diff housing to move thus adjusting the load proportioning valve accordingly.
In a vehicle that carrys a varying load this automatic adjustment of the rear braking force allows more efficient rear braking and overall vehicle braking. In modern vehicles this is done with ABS though there are some weird setups like in the Iveco Daily which uses both.

Which leads me to a couple of questions..................

For a vehicle that carrys a basically constant load (such as an Oka motor home) could the adjustment arm be removed and the adjustment pre set ? This would allow the space taken by the spring/arm assembly to be better utilised eg. for under floor storage or a water tank.

If using adjustable rear air bags (for example) to maintain rear ride height or to assist the springs under load by reducing sag does this reduce overall braking effectiveness by not allowing the proportioning valve to operate correctly ?

Deano.
Last Edit: 18 Nov 2019 07:58 by Dean and Kaye Howells.

Please Log in or Create an account to join the conversation.

More
18 Nov 2019 14:36 #33 by Ralley
Ralley replied the topic: Load Sensing Valve
Like Peter said when you brake hard the front dips and the rear lifts up thus taking weight of the rear, even if you have active airbags in the rear. I imagine if you were to go over a hump or hit bumps in would be of use to affect the brakes in the rear according to the loads being applied at any given moment.
Rob
The following user(s) said Thank You: Dean and Kaye Howells

Please Log in or Create an account to join the conversation.

More
18 Nov 2019 15:50 #34 by Aussie Iron
Aussie Iron replied the topic: Load Sensing Valve
You also need to remember that when you are in the situation of heavy braking and the front dips raising the rear (no matter whether you have constant load or not) that the arm also shifts thus changing the proportion of braking (front to rear) as you are trying to stop.

Dan.
The following user(s) said Thank You: Dean and Kaye Howells

Please Log in or Create an account to join the conversation.

More
18 Nov 2019 19:31 - 18 Nov 2019 19:32 #35 by Alister McBride
Alister McBride replied the topic: Load Sensing Valve
There's a fixed proportioning valve up front (can't remember the percentages) and the variable one at the rear to do the rest of the adjustment. The VS/VT commodore one is metric versus the old 1 tonners' imperial so you need to adapt the connectors on the ends of the pipes if you change over is my understanding... there may be a way of swapping the internals, although if yours is seized i wouldn't as the bore is probably stuffed...
cheers, alister
Last Edit: 18 Nov 2019 19:32 by Alister McBride.

Please Log in or Create an account to join the conversation.

More
05 Dec 2019 17:30 #36 by Peter Davis
Peter Davis replied the topic: Load Sensing Valve
Has the small spring with adjustable bolt been preset at the factory? or have people tinkered with the tension.
With the long spring joining to the diff by chain or cable how much shortening does it take to make a difference.
Or was there a preset length originally from the factory?

Please Log in or Create an account to join the conversation.

  • Peter and Sandra OKA 374
  • Peter and Sandra OKA 374's Avatar
  • Away
More
07 Dec 2019 03:44 #37 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: Load Sensing Valve
Peter the bolt that anchors one end of the spring is your fine adjustment, knowing Oka they just bolted it on out of the box I would imagine.
You can undo the bolt holding the two halves of the arm and slide it to vary the length which will in turn change the braking slightly.
Unless you are changing suspension height drastically from standard it shouldn't be necessary to change the length of the cable/chain too much.
I have seen where the mounting bolts for the valve are slotted allowing the valve to be slid up and down on its mounts but mine isn't slotted.
I made a new cable as mine had frayed and I did make it about 15mm longer which did increase the braking so backed off the adjustment bolt a little bit to compensate.

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 680w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.

Please Log in or Create an account to join the conversation.

More
07 Dec 2019 17:35 #38 by Holmz
Holmz replied the topic: Load Sensing Valve

Peter Davis wrote: Does the brake proportioning valve just decrease the amount of braking to the rear brakes. Or does it effect the front brakes as well. So if it was allowing full flow to rears wouldn't that be the same braking force as the front.


My understanding is..., "just the rears".

Please Log in or Create an account to join the conversation.

Powered by Kunena Forum