[DeTomaso] Brake Areas

[Göran Malmberg]

Anyone have first-hand experience on master-to-caliper piston area
ratios that result in reasonable pedal forces?
Planning to target equal brake bias front and rear as a starting point.
tony DiGiovanna <tonydigi at optonline.net>

TONY,
As I mentioned in my last inlay, F1 cars takes 220 pound of pedal force.
Well, I guess we have to forget that sort of legpower and talk reasonable 
figures. However, we newer get the "touch" feeling of a power assist. But 
there isnt 220 pound of effort just for fun or "show off", It is that the we can
control the ammount of power used.

200:1 is about right for the Pantera owner using a manual brake system.
The pedal ratio is about 5:1, which means that 200/5=40. Master cylinder 
to caliper area should be 40:1 then. 
A 4x1,75" piston caliper makes for an area of 6204mm^2, and we have 
two of them=12408mm^2. We may select 5/8, 3/4 or a 1" master cylinder.
They are 198, 283 and 506mm^2. 12408/198,283or506 makes 62,43 and
25:1 in ratio. 43x5=215:1 in total ratio which suit our needs. The one inch
master gives 125:1 which is very heavy. The 5/8 is 310:1 which may end 
up with floring the pedal if not the system is the very top quality stuff.

The balance frot to rear then. Even if the car has 60% rear weight, we may 
count on the reverse att full braking. So about 40% of the pedal force should 
land at the rear. If both front and rear uses the same caliper 4x1,75 pistons,
we may use a 1 inch master for the rear, but that gives only 37% at the rear.
Maybe a 7/8 rear master should do.

But moost rear calipers are smaller? Right, we should balance the pad area
40-60 for equal heating. And usually the piston are follows the pad area, but
NOT necesarley. But SEPARATE the piston area balance from the pad area
balance, they are two different matters.

If the pad area happen NOT to balance the braking balance, differen material 
pads for different temperature working window will need to be used, and this is
a complex situation to sort out.
Goran Malmberg