Brake proportioning valve adjustment

[GUte]

Finally got my longer brake bias bracket in but have no idea what the correct adjustments are?

Is the spring supposed to be tight, closing the valve or should it be a little looser so the valve is open?

Hope that makes sence lol ??

Im thinking the spring should should be tight so when weight is added to the tray, the spring will loosen and open the valve. If its open, its only going to stay open when the tray is loaded isnt it?

Pretty much no point in even having it if thats the case or am I missing the point?

Cheers for any advice!

[the evil twin]

I think the biasing point is set up as a distance "measurement" when the vehicle is stationary and level no load (spose it would be hard to do if it was moving eh) ROFL

I used to have the distance written down in my old manual but I gave it to the dude who bought the truck. I'll try and find it again but here's hoping someoone else knows off th etop of their head

[YNOT]

If you're fitting the bracket that raises the bias valve attachment point at the diff end then you shouldn't need to adjust the bias valve. Just raise the attachment point the same amount as the suspension lift and it should be very close to right - assuming the bias valve was adjusted correctly before the lift.

Tony

[GUte]

Yes thats the one I am talking about. I didnt check how it sat before doing the lift but there was not much tension on the spring so the valve was open (after the lift). Im pretty sure this allows full power to the rear brakes, never had them lock up so I will probably just leave it like it was but would still hope to get confirmation

Cheers

[robbo71]

You can find a very well explained purpose and the adjustments required for a proportioning valve after a lift kit and it also comes with pictures.

http://www.nissanpatrol.com.au/forum...ence-Document.

Sub quote from the document Message me and I can provide more on the document if you want.

"DO NOT touch the allen head screw on the valve these are pre-set from the factory. The spring needs to measure between 175mm and 178mm end to end of the spring not just the coils. Some will tell you that the spring is self adjusting, meaning that when you lift the vehicle the spring will stay at the correct length, this in fact it actually does with a 2” lift. What changes is the ability of the spring to provide the correct tension at the correct angle. As for higher lifts check out the picture in this section of a GU4 that has a 5” lift, the spring is almost vertical to the BPV lever.

[GUte]

Thanks robbo!

[JoeG]

Hi GUte
I fitted a GVM upgrade and then air bags, the lift was adjusted for but after fitting the air bage there was no rear brakes (as the air bage stop any rear end droop due to load) so when I fit the camper I slip the spring off
(the camper and fuel/water is around 950 kg loaded so need full rear brakes)
So just be aware when and if you fit load assist air bags they have the effect of deducing the rear brake bias
Hope all this makes sense
Joe

[JoeG]

Hi again
when the spring is streached the proportioning valve is open and minimum rear brake pressure
when it is loose maximum rear break pressure!
thats why it is normaly set mid way to give higher pressure on loading up and lower pressure when loose (unloaded or heavy braking and the back lifts)
Joe

[macca]

A test I did yesterday
Chock front wheels, sit back axel on jack stands with wheels off ground. Make sure your in 2WD.
Start engine put in gear, in my case 2nd as its a manual. Release clutch now the rear wheels are spinning.
Stand on brakes to stall engine.
Mine didnt stall so the valve was stopping the rear brakes from being effective.
I want full pressure to the rear so fitted a small bungee to the lever on the valve and redid the test, stalled even at 2000rpm.
Adjusted how I wanted and now have better braking performance. The bungee has some give in it not to damage the valve.
I took the spring completely off.
Hope that makes sense.
JoeG taking the spring off and doing nothing else gives no rear brakes from my experience.
Macca

[macca]

Done a few K's on all sorts of terrain and alot happier wth the braking now.
I'm thinking I will leave it like this as it stops better on the black where a front would lock up.
The spot this happens is off camber down hill in the wet approaching a roundabout.
Scared the cactus out of me the first time it happened. Doesnt do it now.
Macca