23/07/2022
HEL Performance | Brake Doctor
The things that concern us most with brake hydraulics are the following:
Pressure
Is a constant in the hydraulic system. If you put 10 psi into a system hydraulic laws state that this 10 psi will act on all surfaces within the system equally. Pressure In = Pressure Out.
Force
A 1 sq inch master cylinder with 10 lb of force applied to it will produce 10 lb of force per square inch or 10 psi. If the calipers have a surface area of 10 square inches then the force here will be 10 x 10 lb which will mean the calipers produce 100 lb of force. The pressure acting on the system is the same, in this case 10 psi, but the force can be altered by changing the surface area of the calipers.
Fluid Displacement
If our 1 sq inch master cylinder travels forward 1" then the amount of fluid it displaces will be 1 cubic inch. If this fluid is then spread over the 10 square inches of caliper the calipers will only be able to move 1/10th of an inch. You will have huge force (100 lb) but the caliper pistons may not move forward enough to grip the disc tightly and so give a weaker brake. This can be seen to happen on some motorcycles which have a small master cylinder piston and two pot calipers. If the two pots are exchanged for six pot calipers then the surface area increases and the force increases at the caliper BUT the small master cylinder only moves a small amount of fluid which in turn equates to a smaller movement of the caliper pistons
For more information head over to the HEL Performance Brake Doctor Pages at https://www.helperformance.com/brake-doctor
