Final answer:
The correct amount of slack adjuster free travel on a properly adjusted S-cam brake is 3/8 to 5/8 inch (10 to 16 mm), which ensures efficient and safe brake operation.
Step-by-step explanation:
The correct answer is option a) 3/8 to 5/8 inch (10 to 16 mm). The slack adjuster on an S-cam brake system is a critical component that helps to maintain the proper distance between the brake shoes and the drum. Proper adjustment of the slack adjuster is essential for safe and effective braking.
When the slack adjuster is correctly set, it will have free travel —also known as the amount of movement before actual brake engagement— that falls within the recommended range of 3/8 to 5/8 inch. This measurement ensures that the brakes will engage properly without being too loose, which could result in excessive stopping distances, or too tight, which could cause the brakes to drag and overheat. It is important for safety to conduct regular maintenance and adjustment checks on the slack adjusters of S-cam brakes to prevent brake system failure.