What is a critical step in preparing a trailer for winter storage?

Draining all water from the air brake system is a crucial step in preparing a trailer for winter storage for several reasons. Over time, moisture can accumulate within the air brake system, primarily due to condensation. In colder temperatures, this moisture can freeze, leading to potential blockages or malfunctions in the braking system when the trailer is put back into service. By thoroughly draining the air brake system, you mitigate the risk of ice formation and ensure that the brakes remain functional and safe for future use.

While other steps like adding antifreeze or inspecting tires could be considered, they do not address the specific operational hazards presented by winter conditions affecting the brake system. Removing the trailer from the towing vehicle is more of a logistical step that does not directly impact the readiness or safety of the trailer's critical components during winter storage.