[Fot] brake bias / balance

[Mike]

FOT;

I deliberately didn't say what car 'cause I didn't want to unfavorably 
bias the responses <G>. It's a 67 AH 3000 to which we've fitted a brake 
conversion (4-pot calipers, vented rotors) on the front and discs on the 
rear. The question isn't so much about this car, but rather a generic 
question about how to establish what the balance is on any car. The 
specific car becomes an issue when trying to determine how to change the 
balance.

David Talbott wrote:
 >
 > I've seen people use gauges to define the pressures, and they are 
probably very useful to be in the ballpark when you roll off of the trailer.


  Pressure measurements would be a starting point, but pad material ie 
friction coefficient, unless the same front and rear, would negate 
anything you learn by measuring pressures. The seat-of-the-pants method 
seems to be the consensus. We were looking for something 
measurable/repeatable.


Tony Drews wrote:
 > Since part of the setup depends on how much friction your particular 
front and rear pads / shoes have, I don't think there's way other than 
seat-of-the-pants.


   We have installed softer pads in the rear (semi-metallic in the 
front) for exactly that reason; to give the rears more bite. We're also 
very aware of the difference tires make, since that's where all the 
actual work occurs. An interesting note is that stickier tires push the 
bias forward due to increased weight transfer under braking. What we're 
looking for is a measurable, ie repeatable way of determining where the 
balance is now and when we get it right. So far all the response 
advocate seat-of-the-pants adjustments.

    Doing seat-of-the-pants in a race car would be lot easier than 
pushing a car on the street at the 7/10 or more needed to show a 
problem. On this particular car, in a straight line the fronts lock 
first. Does that mean we've got 51% front and 49% rear or 90% front and 
10% rear? By measuring the temps we surmise that it's more like 60% or 
70% front. We'll install a proportioning valve and measure some more 
temps and do lots more driving and adjusting.