G
Guest
·The brake proportioning valve on the 65/66 is an adjustable unit.As to master cylinder choice read this from "hotrodusa.com":
Formula for Master Cylinder Pressure
How do you determine the pressure output of the master cylinder. The following information will help you determine the proper size master cylinder:
To figure how much pressure your master cylinder is putting out:
C = pedal ratio
D = pounds of pressure apply by your foot
E = area of you master cylinder
F = pounds of pressure out of the master cylinder
C X D /(divided by) E = F
Example: If you have a 1" master cylinder the area equals 1/2" x 1/2" x 3.14 = 0.785 Square Inches. So, 100 pounds (of applied foot pressure) X 6 (pedal ratio) divided by 0.785 = 764 pounds of pressure.
If you have a 1-1/8" master cylinder, 100 psi X 6 (pedal ratio) divided by 0.9935 = 604 pounds of pressure.
Here is some info on master cylinder with "constant" of 6 to 1 pedal ratio and 100 psi being applied.
3/4" master cylinder = 1359 psi
7/8" master cylinder = 998 psi
15/16" master cylinder = 870 psi
1" master cylinder = 764 psi
1-1/8" master cylinder = 603 psi
Formula for Pedal Ratio:
Pedal ratio is the ratio of leverage you brake pedal applies to the master cylinder. To determine the pedal ratio you need to measure the height of the pedal to the pivot point then divided the measurement of the pivot point to the lower arm that controls your rod to the master cylinder.
A = height of pedal
B = center to center measurement of the lower arm
C = pedal ratio
A divided by B equals C
Or example 9" divided by 1.5" equal 6 to 1 ratio.
If you apply 100 pounds of pressure to the brake pedal, 100 pounds X (6 to 1) = 600 pounds of pressure. So, if the brake pedal has been modified from its' original design the pedal ratio is effected drastically. You can now see the pedal ratio is a "multiplier" of the pressure you apply with your foot, because this is the leverage that is applied to the master cylinder.
Now, take this same formula and substitute 2" instead of 1.5" you end up with a 4.5 to 1 ratio. Multiply 4.5 times the 100 pounds of applied pressure and you get 450 pounds instead of 600 pound. That half-inch cost you 25 percent of your braking power. The same thing applies when you shorten the upper measurement.
Greg B
Formula for Master Cylinder Pressure
How do you determine the pressure output of the master cylinder. The following information will help you determine the proper size master cylinder:
To figure how much pressure your master cylinder is putting out:
C = pedal ratio
D = pounds of pressure apply by your foot
E = area of you master cylinder
F = pounds of pressure out of the master cylinder
C X D /(divided by) E = F
Example: If you have a 1" master cylinder the area equals 1/2" x 1/2" x 3.14 = 0.785 Square Inches. So, 100 pounds (of applied foot pressure) X 6 (pedal ratio) divided by 0.785 = 764 pounds of pressure.
If you have a 1-1/8" master cylinder, 100 psi X 6 (pedal ratio) divided by 0.9935 = 604 pounds of pressure.
Here is some info on master cylinder with "constant" of 6 to 1 pedal ratio and 100 psi being applied.
3/4" master cylinder = 1359 psi
7/8" master cylinder = 998 psi
15/16" master cylinder = 870 psi
1" master cylinder = 764 psi
1-1/8" master cylinder = 603 psi
Formula for Pedal Ratio:
Pedal ratio is the ratio of leverage you brake pedal applies to the master cylinder. To determine the pedal ratio you need to measure the height of the pedal to the pivot point then divided the measurement of the pivot point to the lower arm that controls your rod to the master cylinder.
A = height of pedal
B = center to center measurement of the lower arm
C = pedal ratio
A divided by B equals C
Or example 9" divided by 1.5" equal 6 to 1 ratio.
If you apply 100 pounds of pressure to the brake pedal, 100 pounds X (6 to 1) = 600 pounds of pressure. So, if the brake pedal has been modified from its' original design the pedal ratio is effected drastically. You can now see the pedal ratio is a "multiplier" of the pressure you apply with your foot, because this is the leverage that is applied to the master cylinder.
Now, take this same formula and substitute 2" instead of 1.5" you end up with a 4.5 to 1 ratio. Multiply 4.5 times the 100 pounds of applied pressure and you get 450 pounds instead of 600 pound. That half-inch cost you 25 percent of your braking power. The same thing applies when you shorten the upper measurement.
Greg B
