Brake Bias System on Utes....anyone familiar with it?

Submitted: Wednesday, Jan 23, 2013 at 14:30
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Hi everyone, I have just bought a 2008 Nissan Navara RX Ute. It has ABS with front disc & rear drum brakes. I have been told it has a "Brake Bias Device" fitted as standard. Apparently most utes have them. My understanding of the device is,as you load the rear of the ute up...the downward pressure causes this device to alter how the rear brakes work. The opposite happens when you use a WDH (towing van) which I plan on doing. I have been told by a good mate that when he towed his van,he used WDH on his 2004 Navara. He told me he actually rear ended a car because the rear brakes on his Navara didn't seem to work & he only had braking on his front wheels causing same to lock up. I plan on using my Navara to tow our large van & I am concerned that when using the WDH I might be interfering with some "Nissan" braking system. I have phoned Nissan & was told that nearly every ute has this "Bias" system & they had no idea what affect a WDH would have on the "Brake Bias". There is no mention of this device in my owners book. I would appreciate any advice. Also question for Navara owners,how do I know if the vehicle has a LSD fitted? Thanks Robert


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Reply By: Nomadic Navara - Wednesday, Jan 23, 2013 at 14:53

Wednesday, Jan 23, 2013 at 14:53
I doubt that your mates accident would have been caused by the "brake bias." The system is there to reduce brake lock-up when the rear wheels are lightly loaded. When you tension up the WDH bars you lighten the load on the rear wheels and thus need to limit the likelihood of brake lock-up and thus retain the maximum possible braking.

There is a possibility your mate has over zealous in the tensioning of his bars and has reduced the traction on the rear wheels too much. Other possibilities are intention, following too closely or insufficient braking on his trailer.

I have had no problems with braking with my D40, I use WDH. I have however had brake problems with my van but that has been fixed. I would no play with the brake bias, this could increase the tendency for brake lock-up and giving the ABS more work to do.
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Reply By: bluefella - Wednesday, Jan 23, 2013 at 15:27

Wednesday, Jan 23, 2013 at 15:27
I had a 2003 navara 3.0td 4X4 fitted with nissan towbar, on either the bar or in the manual it stated not to use WDH. Can'nt remember which.
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Follow Up By: bluefella - Wednesday, Jan 23, 2013 at 15:30

Wednesday, Jan 23, 2013 at 15:30
from memory it was use of WDH could twist the chassis?
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Follow Up By: Nomadic Navara - Wednesday, Jan 23, 2013 at 16:00

Wednesday, Jan 23, 2013 at 16:00
Most of the twin cabs with broken chassis were fitted with air bags, were towing or carrying large loads and not using WDH.

The advice Was "not recommenced on Nissan bars." This came about when a couple of bars on Pathfinders (not utes) fell off because of the twisting from WDH. Nissan made no mention of WDH being used or not being used on other manufacturers bars.
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Follow Up By: NTVRX - Wednesday, Jan 23, 2013 at 22:33

Wednesday, Jan 23, 2013 at 22:33
There isn't a warning on the bar about WDH. Only the capacities for towing & another warning not to exceed the Nissan criteria for towing.
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Reply By: Ross M - Wednesday, Jan 23, 2013 at 17:04

Wednesday, Jan 23, 2013 at 17:04
NTVRX
As people have mentioned , the van should more than compensate for it's own weight so the overall braking should be either, the same stopping distance or better.
Even with a WDH fitted they shouldn't be hauled up too far so as to reduce the weight on the rear wheels to a high degree.
The weight of the van will when braking, take over the WDH's normal help and it will be forcing the tow bar down because of the transference of the weigh/ mass of the van under braking. A rolling van with the brakes suddenly applied will increase it's tow ball weight significantly.
If your mate has a 2004 Navara it will most likely still have the original shock absorbers.
These are vital things required to control the suspension while under braking. and steering and to control pitching while towing.

Only the tyres grip on the ground will provide the retardation force required.
If the tyres bounce and flutter on the road surface, then they aren't controlled well and the braking distance becomes longer, despite having ABS, big new tyres and a big foot on the pedal.
Most shockers on modern utes are selected comfort and to control the average mass of the vehicle, if loaded they probably won't perform as well.
If they have done over 40,000km then throw them away because they will now be a liability if and when the increased performance (which they haven't even got when new) is now required to keep all under control.

Most people, and their mechanics, don't seem to ever consider the shock absorbers and they are, after the grip of the tyres, the most important part of your vehicle.

Not many utes of today or yesterday ie 2004, do not have shockers suited to any type of emergency maneouvre let alone an emergency maneouvre while towing.
Correctly loaded with a WDH suitably attached the vehicle won't stop well if the said shockers are not up to the task.
AnswerID: 503222

Reply By: gbc - Wednesday, Jan 23, 2013 at 19:23

Wednesday, Jan 23, 2013 at 19:23
Check your manual, lots of 2008 utes had EBD (electronic brakeforce distribution) which negates the need for a brake bias valve.
Your mate is spot on, and anyone who tells you otherwise has no clue.
Bias valves operate simply by forcing a valve open or shut relative to the rear axle's position to the chassis. Have a look for a transverse rod mounted on the rear axle, running to a valve mounted on the chassis.
A brake bias valve is also tricked by airbags, and heavy duty or higher suspension lifts that change the geometry of the arm relative to the way a factory standard ute would react to a given load.
The braking system will always allow full power to the front brakes, but the bias valve, when operating will bypass brake fluid from the rear drums and that is where the real stopping power is (hence why they need to be retarded on an empty ute). A WDH will trick the bias valve into thinking the ute is empty, and will rob it of valuable stopping power - there's no way it can't do this. The whole system is rudimentary, but is there for a very important reason. If you NEVER drive the ute empty it is easy enough (and illegal) to cable tie the actuator, or extend the mount, neither of which is recommended - the best way is to not use a WDH. If you've ever sailed straight through a set of lights in the rain with the rears locked up on a ute you'll understand the importance of a WDH.
Luckily this stuff is pretty much old tech these days. 2008 was when I chose a Colorado for towing and specifically because it had EBD for towing - it is amazing compared to the alternative.
AnswerID: 503230

Follow Up By: NTVRX - Wednesday, Jan 23, 2013 at 22:44

Wednesday, Jan 23, 2013 at 22:44
My mate also told me that he had cable tied his "Brake Bias" so it would seem a load was on the rear. He used a WDH. He did not have ABS,,which mine has. I am still trying to find out if it has EBD. Are you suggesting gbc that I cable tie the Brake Bias & use WDH...I'm a bit confused by your comparison. Thanks everyone for the replies.
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Follow Up By: Nomadic Navara - Wednesday, Jan 23, 2013 at 22:58

Wednesday, Jan 23, 2013 at 22:58
Quote "A WDH will trick the bias valve into thinking the ute is empty, and will rob it of valuable stopping power - there's no way it can't do this."

How do you work that one out? To make the bias think the ute is empty you would have to lift the back up to at least the the level it would be without anything in the tray and the van not hitched.

In the real world there is a fair bit in the tray. This compresses the rear suspension somewhat. Then when you hitch the van and tension the WDH bars the rear suspension is a little further compressed. This will give a true indication to the braking system that there is a load on the back of the tug. I don't think you have thought the situation out properly.

On the matter of "the best way is to not use a WDH" that will reduce the braking available on the front axle. Good braking on the front axle is paramount. If you don't have WDH then a considerable amount of weight is removed from the axle. This will decrease the amount of braking available.

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Follow Up By: gbc - Thursday, Jan 24, 2013 at 06:11

Thursday, Jan 24, 2013 at 06:11
How do I work what out?
A WDH is now not used to move the centre of effort from ball weight forward along a chassis? Give me a break.
The key point here is not to 'guess' what's in the tray, or guess if the WDH has allowed the rear to compress a bit. It's to understand how a factory standard ute on factory standard springs with no WDH would sit with the same van on the back and load in the tray. Sagged down like a mangy dog is the most common answer, and in that position braking effort (BIAS) is moved from the front to the rear of the vehicle, and rightly so.
Good braking on the front is inportant, I agree, but when performing an emergency stop towing a big trailer and ONLY the fronts lock up or work because the bias valve won't allow the rears to grab, how do you think it's going to end? Believe me, I've found out the hard way how they work/don't work, as have plenty of others, hence why the actuator gets cable tied to the chassis when towing with modified suspension, airbags, WDH's or anything else that does not give a true indication of how much traction is available to the rear wheels.

NTVRX - I'm not going to tell you what to do, but I'll tell you that my last vehicle ('03 hilux SR5) had airbags on the rear (dual cab, towed all over the country, didn't snap - amazing) which also assist a vehicle to maintain a proper attitude when towing. I will also tell you that it had a 2" lift kit. When I installed the lift kit, I purchased (separately) a brake bias extension which moved the lower (axle) mounting point 2" higher so that braking wasn't compromised when the ute was empty. However, it soon became abundantly apparent that when carrying load, or towing load and using the airbags/HD springs to assist, the lack of rear bias made the vehicle dangerous. From then on, when towing any distance, it was common place to undo the brake bias arm and cable tie it up under the tray. The difference had to be felt to be believed.
In your case I believe this argument will be moot, as I am pretty confident that if you have ABS, you get EBD and BAS anyway in the D40's.
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Reply By: Rockape - Wednesday, Jan 23, 2013 at 19:52

Wednesday, Jan 23, 2013 at 19:52
NTVRX,
easy way too find out if you have an lsd is park on your lawn or someone else's you don't like, then tramp it. You will soon see the result. One wheel tearing up your lawn or 2.

AnswerID: 503237

Follow Up By: Bushranger1 - Wednesday, Jan 23, 2013 at 20:07

Wednesday, Jan 23, 2013 at 20:07
Yea I guess thats one way to check it! LOL.

Another way is that there is usually a sticker next to the rear diff filler plug indicating that the vehicle is fitted with an LSD.
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FollowupID: 779884

Follow Up By: Rockape - Wednesday, Jan 23, 2013 at 20:41

Wednesday, Jan 23, 2013 at 20:41
Bushy,
I have seen those same stickers on Toyota diffs and we know what that means. This is an LSD equipped vehicle sucker. Ha.Ha.

I got caught the other day in my new Ranger which has a diff lock, hell you have to push the button. Well I accustomed to my old troopie with the detroit lockers. Damn. I left one really nasty one wheel divot up a bank.

RA.

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Follow Up By: NTVRX - Wednesday, Jan 23, 2013 at 22:38

Wednesday, Jan 23, 2013 at 22:38
Yep,already had that thought RA.....I thought but haven't looked at diff housing didn't know if there was another code somewhere. Nissan book is filled with......"Where fitted" alongside listed components!!! Useful as an ashtray on a motor bike!!!
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FollowupID: 779904

Follow Up By: NTVRX - Wednesday, Jan 23, 2013 at 23:03

Wednesday, Jan 23, 2013 at 23:03
Had a visit to Red Book & found my model listed & the list of standard equipment matches my vehicle to a T. There was no mention of LSD however EBD is listed as standard. Rob
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FollowupID: 779909

Reply By: mountainman - Thursday, Jan 24, 2013 at 05:51

Thursday, Jan 24, 2013 at 05:51
i have a 40's landcruiser.
and i can tell you with the lpsv load porpotioning sensor..... not correctly adjusted WILL cause an accident.
and the same setup as said on all utes.
my rear drums wouldnt come on, only when i locked the front up, on a wet road, doing like 40k's/h and it wouldnt pull up, i knew it was the lpsv.
my option was longer bolts and few nuts under the arm that holds the rod, and went for a drive on a country dirt road and locked them up, i HAVE BRAKES NOW!
she pulls up realy well.

your option is to adjust the sensor a little to come on when empty tray, and get better braking.

cheers hj47 cruiser
AnswerID: 503261

Follow Up By: NTVRX - Thursday, Jan 24, 2013 at 12:01

Thursday, Jan 24, 2013 at 12:01
Thanks everyone for taking the time to respond to my post. Robert.
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