Braking Bias Adjuster

[patpur]

Question for you guys - I bought my car used last January and there was little documentation on the car. I have sorted through a lot of things but one of the questions that still remains is how does this gizmo work. Mine appears to be from Wilwood and it has an increase and decrease arrows on the dial. I know it is supposed to move the braking from front to rear but which way is which? My understanding is that these devices are used on track cars. Any thoughts for the street? I don't do the track, at least not yet. I ask because I don't want just start turning the dial and screw up my braking. These brakes (4 wheel King Cobra discs) have always felt a bit odd to me but I wrote that off to the fact I'm used to power discs in the other cars I've driven. My Cobra brakes are not power assisted. I have included a picture of the adjuster which resides in my trunk up by the drivers' roll bar. Thanks for any help with this.3228

[rich grsc]

It works by decreasing pressure to the rear brakes. Usually not needed, as more rear brakes are needed, not less. I would start by fully opening the valve, turn in the (-) direction. Remember it is designed to decrease pressure so turning it to (+) give less pressure to the rear.

[patpur]

Thanks Rich.

[Greg_M]

It works by limiting pressure to the rear calipers The pressure will build normally to the rear brakes until the setpoint is reached. At the setpoint, additional fluid pressure from the master cylinder does not pass through to the rear brakes.

From Wilwood:
Proportioning Valve Adjustment: The proportioning valve is used to adjust the rate of increase in rear brake line pressure, relative and proportionate to the increase in front brake line pressure. For safety and performance, the rear brakes should never lock before the front brakes. Otherwise, an out of control situation could occur.
1. Begin with the valve in the full proportioned (least pressure) position by turning the knob all the way out (counter-clockwise rotation).
2. In a safe location, make several hard stops from 30 MPH observing the function of the rear brakes. If the rear brakes do not lock up before the front, gradually increase the rear line pressure by rotating the valve clockwise (two turns each time).
3. Continue these adjustments until the maximum amount of rear brake pressure can be achieved, and no wheel rear lock is observed.
4. Test the vehicle again at 50 MPH and make any additional adjustments as needed.

As stated most people don't need one in the rear as these car usually need more rear brakes than they have.

Greg

[Jeff Kleiner]

If memory serves even with the valve set for maximum pressure (fully clockwise) there is still a reduction in output line pressure vs. input.

Jeff

[Greg_M]

This is true. They still reduce pressure by about 100 psi.

Greg

[snakeboost]

Check how it is plumbed........I have some customers using them on the front lines.
Steve

[Pierre B]

I understand the first few trial runs to test original bias are best done on a slightly gritty road surface. That will help the tires break traction at slower speeds, thus giving a safer indication of lockup tendencies.

[patpur]

So I need to see if the adjuster is hooked up to the front or rear brakes? That is something I don't know.
Thanks for all the input.

[d42davis]

Obviously, from it's mounting location, it is in the rear brake circuit. Unless you have huge brakes in the back, you need more rear braking, not less. The valve provides some benefit to nose heavy Mustangs but has questionable value in our cars, which need approximately twice as much rear braking as a standard Mustang. Anything that decreases rear braking is a bad thing.
DD