What is a common sign of impending brake failure in trucks?

A spongy brake pedal or reduced stopping power is a critical indicator of impending brake failure in trucks. When the brake pedal feels spongy, it suggests that there is air in the brake lines, a possible hydraulic fluid leak, or that the brake system is losing pressure. This condition can significantly diminish the effectiveness of the brakes, making it harder for the driver to stop the vehicle safely.

Additionally, reduced stopping power can result from worn out brake pads, malfunctioning brake components, or issues with the braking system, all of which pose serious safety risks. Recognizing these symptoms early allows drivers to take necessary actions to inspect and repair the braking system before any potential failure occurs, ensuring the safe operation of the truck.

The other options do not directly indicate brake failure and are related to different issues, such as engine performance or tire condition.