To keep this brief, I'm looking at brake options and have a question on figuring brake bias.

So the Maxima's proportioning valve has a split point pressure of 284psi, with a reducing ratio of .2

Does this mean that above 284psi the Rear pressure raises 20 percent less than the front? (or you could read that as 80 percent of the front pressure)

Or am I thinking backwards and the pressure only raises 20 percent of the front. That to me seems too small, but what do I know, I don't design these things. I guess it depends on how hard of braking 284psi is.

Can anyone verify exactly how this math works with certainty.

Also, as a long shot, can anyone quantify 284 psi? Is that like late braking, or standing on them before you hit the old lady in the Cadillac.

 

at pedal pressures lower than 284psi, the pressure to front and rear brakes are equal.
above 284psi, as the pressure goes up 10psi in front, it only goes up 2psi in the rear.

this is to counteract the fact the car's weight is shifting to the front under hard braking, so the fronts need to do more work that harder you're on the brakes.

As for quantifying 284psi on brakes... that's a 'decent' stop. much harder and the car will begin to nosedive. full-on, almost-locking-the-brakes application is around 1000psi.

 

Awesome, Exactly what I wanted to know. Thanks Matt.

 

That's really cool--always wondered how the proportioning valve worked.

Funny, BMW had advertised this system (50/50 then like 70/30 under hard braking) as something unique to them a few years ago...

 

Some of the newer Nissans have the Electronic Brake Force Distribution system now, where I think each wheel is electronically controlled depending on several conditions. That's one of the reasons why when the Z and G came out they were kicking butt in braking distances. It's getting so much more sophisticated these days.

 

I've asked a similar question before and what i gathered from it is that EBD only affects brake balance between L and R, specifically the rears, not front and back.

At least that's how it supposedly is on 2002 Maxima's anyway.

 

Here's what I found on a Nissan website a while ago:

 

Nissan's been doing it for decades... look at the rear subframe on 92-94 SE Maximas w/ abs (it was an option)... they have small bias adjusting valves attached to each side in the rear to account for body lean and cargo load in the trunk. the lower the car sits, the more rear brake it gets.