In the 'at rest' position, what occurs with the primary and secondary pistons?

When a braking system is in the 'at rest' position, the primary and secondary pistons move forward to ensure that the hydraulic circuit is sealed. This sealing is crucial as it prevents any loss of hydraulic fluid, which is necessary for effective brake application when the vehicle is in motion. The forward movement of these pistons maintains pressure within the braking system, allowing for a quick and responsive reaction when the brakes are engaged. This positioning serves to keep the brake components ready for immediate application without any leakage that could lead to brake failure.