Was curious one day about how much force was seen at different locations in the brake system so I took some measurements and did some math for the 97-01 Preludes. This is what I found. Might have made a mistake somewhere in the math but I hope we can get it right and maybe even sticky?










Force Applied Via Pedal to Booster:
With 70 Lbs. Applied to Pedal:
70Lbs. x 3.67:1 = 257 Lbs. Applied to Pushrod of Booster

With 100 Lbs. Applied to Pedal:
100Lbs. x 3.67:1 = 367 Lbs. Applied to Pushrod of Booster

Booster Output Force:
With 70 Lbs. Applied to Pedal:
70 Lbs. x 3.67:1 (Pedal Ratio) = 257 Lbs. Applied to Booster + 801.36 Lbs. of Booster Output Force = 1,058.36 Lbs. Applied to Master Cylinder Piston

With 100 Lbs. Applied to Pedal:
100 Lbs. x 3.67:1 (Pedal Ratio) = 367 Lbs. Applied to Booster + 801.36 Lbs. of Booster Output Force = 1,168.36 Lbs. Applied to Master Cylinder Piston

Master Cylinder Output Force:
With 70 Lbs. Applied to Pedal:
1,058.36 Lbs. x 0.79 Sq. In. (Master Cylinder Piston Surface Area) = 836.11 PSI to Outputs

With 100 Lbs. Applied to Pedal:
1,168.36 Lbs. x 0.79 Sq. In. (Master Cylinder Piston Surface Area) = 923 PSI to Outputs

Force @ Front Brake Pads:
With 70 Lbs. Applied to Pedal:
836.11 PSI Master Cylinder Output / 4 = 209 PSI (Output Per Wheel) x 3.94 Sq. In. (Piston Surface Area) = 823.46 Lbs.

With 100 Lbs. Applied to Pedal:
923 PSI Master Cylinder Output / 4 = 230.75 PSI (Output Per Wheel) x 3.94 Sq. In. (Piston Surface Area) = 909.2 Lbs.

Force @ Rear Brake Pads:
With 70 Lbs. Applied to Pedal:
836.11 PSI Master Cylinder Output / 4 = 209 PSI (Output Per Wheel) x 1.39 Sq. In. (Piston Surface Area) = 290.51 Lbs.

With 100 Lbs. Applied to Pedal:
923 PSI Master Cylinder Output / 4 = 230.75 PSI (Output Per Wheel) x 1.39 Sq. In. (Piston Surface Area) = 269.75 Lbs.

 

I have since learned that the booster is a "dual" style, not sure what that means for output force @ given pedal pressure & vacuum...does it double? I'm already getting pressure calculations that seem right, like they are on the high side and match what most cars have so doubling it sounds wrong.

Also, on the pressure calculations for the master cylinder output, I divided the total by 4, assuming the total pressure would be evenly applied evenly and equally to all 4 wheels but this is not accurate. There is a proportioning valve that regulates brake pressure between the front and rear circuits. I need more info on what the percentage is between front and rear, then I can make the changes to the numbers from there.