Adjusting Brake sensing proportioning valve (BSPV)

[june]

Just reading through the Nissan Patrol Manuals and thought this might benefit others, the following document- Nissan Patrol Reference Document discusses a bit of everything, but, the bit I found useful and which I have just performed is to do with the BSPV.
It states, if you have a lift on your vehicle (whatever the lift) the BSPV needs to be raised to meet that lift. If this is not done, you won't have any assistance from the back brakes when pulling up, especially if vehicle is heavily loaded. It gives you spring measurement, angles(showing relation of spring to arm) and pictures, eg, I have a 2" lift, so raised the arm 2". Just took it for a brake test run and could not believe the difference it made, I don't think my rear brakes have been working properly since the lift went in about 8 years ago.
It was simply a matter of undoing the arm and putting a bit of flat metal in and therefore raising the arm up, assuring the spring measurement and angle were correct.
I hope this helps others

[Cuppa]

When I got my GVM upgrade done (which included a 2" lift), one of the things done as part of the setup was adjusting the brake proportioning to give a bit more of the braking to the rear wheels. At first the idea of increasing the proportion of the braking to the rear (& corresponding reduction to the front) just didn't seem logical to me, given the increased carrying capacity. ....... But it seems to work ok. It had to as it had to pass a series of braking tests, both stationary & dynamic, before the upgrade could be passed. I can't say that it improved the braking, but with the extra weight on board it seems much the same. Apparently one of the things that had to be avoided was too much 'nose dive' under heavy braking, together with a 'return to level position' without bucking & carrying on. This was achieved by using longer than normal front coil springs together with the brake portioning adjustment, with the view that with extra weight over the rear axle that this too helps to ensure better grip under heavy braking conditions.
I can't recall what the standard pro portioning ratio is between front & back, but would gues it would be something like 60/40.
I think it is now closer to 50/50.
Not something to muck around with unless you have a good idea of what you are doing though.

Cuppa

[nissannewby]

It doesn't reduce the force applied to the front. It only changes what is applied to the back. Hence why it will allow greater braking when a load is on the back and as you said you have more weight on the back now so a little extra traction, so more breaking force can be applied and also as you said it then keeps the car more stable under heavy braking in most conditions

[BigRAWesty]

Thus why you should install a bracket to lower the valve back to standard hight, or you will have less rear brake threw the load range compared to stock setup..

Kallen Westbrook
Owner of
Westy's Accessories (http://www.nissanpatrol.com.au/forums/showthread.php?15134-Westy-s-Accessories.-A-small-back-yard-builder.)

[june]

until i did this mod vehicle would nose dive big time and under heavy braking would take a lot of road to pull up. since fitting bracket vehicle stops in a shorter distance with minimal nose dive.