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

Submitted: Wednesday, Jan 23, 2013 at 14:30

ThreadID: 100141 Views:6660 Replies:6 FollowUps:11

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NTVRX

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

Reply By: bluefella - Wednesday, Jan 23, 2013 at 15:27

Reply By: Ross M - Wednesday, Jan 23, 2013 at 17:04

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.

FollowupID: 779906

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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FollowupID: 779907

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.

FollowupID: 779918