What is the slack adjuster angle for the right rear brakes when released?

The correct answer is that the slack adjuster angle for the right rear brakes when released is typically 90 degrees. This is important for understanding the mechanics of the braking system on a school bus, as the slack adjuster plays a crucial role in maintaining the proper tension on the brake shoes against the drum.

When the brakes are released, the slack adjuster should ideally be positioned at a right angle (90 degrees) to the push rod. This indicates that the system is effectively set to allow for full release of the brakes, ensuring that the shoes do not drag against the drum, which could lead to increased wear or overheating.

Having the slack adjuster at 90 degrees when the brakes are released also plays a role in the automatic adjustment mechanism. This setup ensures that as the brakes are applied and released, the system can appropriately compensate for wear over time, maintaining optimal braking performance and safety.

A different angle, such as those stated in the other options, would suggest either that the brakes are not fully released or that there is an adjustment issue, both of which can compromise safety on the road.