Why should a driver never push the brake pedal down hard while the vehicle's spring brakes are already applied?

Question

Accepted Answer

Combining the spring force with the added air pressure from the pedal could damage the brakes, even though some systems are designed to prevent this

Answer

It will automatically release the spring brakes early

Answer

It has no real effect because the pedal is disconnected from the system when spring brakes are set

Answer

It will cause the governor to cut out the compressor