As just explained, the brake master cylinder (also called master cylinder) is controlled by the kart's brake pedal via a system of levers and tie rods. The driver imparts the braking force by pushing the pedal with a force that can reach up to 40-50 kg. At that point, the force, multiplied by the ratio to the pedal, is transferred to the piston inside the pump, which puts the brake fluid under pressure (which we have already explained in the article “Technique | brake fluid"
). In most braking systems, the piston is driven by compression, i.e. the rod pushes the piston, while in some systems the rod works based on traction, pulling the piston towards the front of the pump (moreover, there are braking systems which have both types of drive, to learn more read "Technical Focus | LKF13 and LKF14, the braking systems with the "two-in-one" master cylinder by Lenzokart"
The force on the piston rod and the brake fluid pressure are related by the equation P = F / A. Where: P is the pressure of the brake fluid, F is the force exerted on the piston rod and A is the internal diameter of the pump, given that it generally varies from 13 to 22 mm (with the same boundary conditions, the greater the diameter of the master cylinder the greater the force required to brake the kart, but the smaller the stroke). The liquid then transfers the pressure to the pistons housed in the calipers, net of pressure drops in the hydraulic circuit. The friction force between the pads and the disc therefore acts on the wheels, decelerating the wheels and the kart.[A]
Assuming that the piston is driven by thrust, when the driver presses the brake pedal, the rod pushes the piston by means of the control lever, until this closes the hole and stops the passage of liquid from the chamber to the tank; the continuous movement of the piston then generates pressure in the chamber and therefore to the ducts directed to the brakes on the wheels. The piston has a longitudinal cable, which works radially with the gasket housing, so that the pressure of the chamber is applied to the internal diameter of the gasket, pushing it against the cylinder walls, thus increasing its seal.