[Fot] brake bias / balance

[David Talbott]

Mike

Not sure about a street car, but on a race car the seat of the pants approach
usually works pretty well by gradually working the bias to the rear and
sensing the response.  On the other hand, if you're having a hard time feeling
much difference you can crank it all the way aft and go find a corner where it
is safe to do a turn-in spin.  The stability problem usually is more
pronounced on corners where you carry your braking into the turn-in, and/or
when the corner entry is downhill - hence accentuating pitch and further
unloading the rear.

The object is usually to get as much help from the rears as possible, but not
so much that the car tries to swap ends on the kinds of corners where your
braking is not all in a straight line.  Over time you can usually get
comfortable with the squirreliness of more rear bias, and remember that with
rear drum brakes, in the course of a race they will often loose more
effectiveness than the fronts, so they can handle more rear bias without
impacting stability.

On the scientific side, I've seen people with gauges to define the pressures,
and they are probably very useful to be in the ballpark when you roll off of
the trailer.  I'm more inclined to think that the proof is in the pudding, and
especially if there are other changes occurring (such as chassis adjustments),
notwithstanding what the gauges say you've got to fine-tune it on track for
the day and the driver.

Dave

David Talbott, President
Architectural Reproductions, Inc.
Portland, Oregon
Toll Free (888) 440-8007
www.archrepro.com
  ----- Original Message -----
  From: Mike
  To: fot at autox.team.net
  Sent: Wednesday, April 04, 2007 6:13 AM
  Subject: [Fot] brake bias / balance


  FOT;
     We're doing some brake mods to a street car and questions started to
  arise about brake balance / bias.
     While it seems the optimum situation calls for a slight (5%-10%)
  front bias, how do we determine where it is now? Temp readings on the
  discs seems to give numbers all over the place, but seem to settle
  around 450F in the front and 250F in the rear. Does this mean we have a
  60/40 split? Is this an effective way to measure bias? When setting up a
  street or race car how do you determine how much to adjust the balance?
  Seat of the pants and what works best? Or is there a 'scientific' approach?

  Mike Engard
  _______________________________________________
  Fot mailing list
  Fot at autox.team.net
  http://autox.team.net/mailman/listinfo/fot