How do you test a trailer's brakes while stationary?

Answer: A — Build system pressure, apply the service brakes, and ensure the brakes engage fully without dragging.

Testing a trailer’s brakes while stationary centers on confirming the brakes can be actuated reliably when the system is pressurized. Start by building system pressure to the normal operating level so the brakes have something to respond to. Then apply the service brakes and watch how the trailer brakes engage—they should come on solidly. Finally, release the brakes and verify there’s no residual drag; the wheels should spin freely once released. This approach directly checks that the brake components (calipers/shoes, slack adjusters, lines, valves) are functioning and properly adjusted. Relying on other cues like sounds or lights isn’t enough, and moving the trailer to test at speed isn’t safe.