When an S-cam brake is correctly adjusted, when will the brake lining contact the brake drum?

The correct answer indicates that when an S-cam brake is properly adjusted, the brake lining contacts the brake drum before the brake chamber has moved halfway through its maximum stroke. This timing is crucial for effective braking performance and safety.

When the S-cam brake mechanism is activated, the pushrod connected to the brake chamber begins to extend. The S-cam rotates to push the brake shoes outward, pressing the brake lining against the drum. For the brake to function efficiently, the contact between the lining and the drum should happen relatively early in the stroke. This ensures that any necessary adjustments can be made to account for wear and that the brakes will respond rapidly once applied.

If the lining were to contact the drum only after the chamber has moved closer to its maximum stroke, it could result in delayed braking action and increased stopping distances, which are less safe. Proper adjustment helps ensure that the brake system performs reliably, especially in emergency situations where immediate braking is necessary.