If air brake systems are not applying and releasing properly, causing grabbing or dragging, what might be the cause?

If air brake systems are not applying and releasing properly, leading to issues like grabbing or dragging, one key cause could be defective supply system components. The supply system in an air brake setup includes critical elements like the air compressor, the air lines, and the brake chambers. Any malfunction within this system—such as leaks, blockages, or failure of the compressor—can disrupt the flow of air necessary for the application and release of the brakes.

When components fail, they may not deliver sufficient air pressure to the brake chambers or may allow air to escape when it shouldn’t, causing the brakes to not function as designed. This can result in brakes that engage too aggressively or fail to release completely, which is evident in symptoms like grabbing or dragging.

In this context, while other options can affect vehicle performance, they do not directly relate to the air brake system's application and release. For instance, unbalanced tire pressure can cause vehicle handling issues but does not impact air brake functionality, and incorrect brake fluid type applies primarily to hydraulic brake systems, which do not relate to air brakes. Worn-out brake shoes may contribute to poor braking performance but wouldn't typically cause issues with the application and release mechanism of air brakes themselves. Therefore, the most pertinent cause is