Measuring brake bias?
 

Hi everyone, I'm just researching for some advice/heads up on what the correct brake bias % set up is? I have the std on board Wilwood brake bias adjuster. 6 pot fronts and 4 pot rears.

I have some V8 Supercar brake bias gauges that I can hook up to the front and rear calipers simultaneoulsy to measure relative brake pressure. A nifty bit of gear.

What I want to know is what setting should I start out with from the get go cold? 50/50 f to r or 55f to 45 r or ???

The car is 1200kg wet with driver and is only used for track day racing no street driving. I'm just interested to hear any thoughts?

Thanks in advance.

Spookypt

I think that it would be a bit difficult to predict the handling characteristics by a specific percentage.

Is your bias a hydraulic pressure adjuster, or is it mechanically moving the pivot in the break pedal and adjusting pressure on two master cylinders.

I would think that as you drive and the brakes heat up it may cause you want to make minor changes.

I too would love to know how much one needs to tweek the adjustment while driving and braking hard.

I've just installed a system on my car, remote cable adjuster to the brake pedal with two side-by-side master cylinders. Have not driven/tested what I've done as of yet.

Arthur

Arthur, thanks for responding... My adjustor type is the mechanical moving pivot in the break pedal and adjusting pressure on the two master cylinders.

I agree with what you're saying, I guess then to set them up you just start at 50/50 and adjust after that as required....

Some seasoned racers/mechanics may be able to shed more light?

Spookypt

Spookypt,
Setting the right brake bias involves so many factors that it is not practical to give a single correct pressure differential number for your car. In fact, during a race, the need for brake bias can change. Thus cars like mine have an adjustment knob for that purpose in easy reach of the driver.

But for a starting point, here's my recommendation and logic. First, you want the front brakes to lock up before the rears for two reasons. This assures you get full braking from the fronts (the more effective brakes) before anything locks up. Also, a car with locked front brakes is less likely to unexpectedly change directions (i.e., spin) than one with locked rear brakes.

Second, the dynamic weight transfer that occurs when applying the brakes effectively adds weight and grip to the front tires while taking weight and grip from the rear tires. The harder you decelerate, the greater this effect. This means you will be able to apply much more braking force (without locking) to the front brakes than to the the rears. For these reasons, I suggest you start with a pressure bias of about 65-75% to the front.

About the only other thing you can do before you actually try out a setting on the track is to test your brakes in a safe place. Get the car up to 40 MPH or so and press the brakes hard enough to briefly lock them up. It might be helpful to have a friend watch your car from a safe place at the road side. If the rears lock up first, increase the bias to the front and try again. If the fronts lock up first, decrease the bias until the rears lock up first, and then bump the bias back to the front just a little.

Good place to start. When I had the mechanical pivot, I put the car on jack stands and had someone slowly press the brake pedal. When you could no longer turn the front wheel, go to the rear and there should be very little resistance. This is only a starting point and should be fine tuned from there.

Ford ranger ,trucks and I am sure others have a valve in the rear brake line hooked up to the suspension., which operates like a crude rear antilock brake system. The more front weight transfer the less fluid , or should I say pressure goes to the back. I would use one of these in preference to manually adjusted bias valve.

I have seen these on Cobras before and they seem like a great idea. I have a 4000 series Cobra with the original style pedal box. It's been a while since I thought about the brake cylinder configuration down there and wonder how difficult it is to install. Can any of you give me some feedback on installing one of these? Thanks!

Get some brake temperature paint, an paint the rotors in a H pattern on the rim or outer vanes of the rotor.....start at 900*, 1000*, 1100*, and 1200*.......

Run the car on the track an come in and see what temp burned off.....front to rear.....that will tell you what to do......