What type of brakes are most commonly used in foundation brakes at each wheel?

The s-cam drum brake is the most commonly used type of foundation brake at each wheel, especially in larger vehicles such as trucks and buses. This type of brake operates based on the principle of leverage, utilizing an S-shaped cam that rotates to push the brake shoes against the inside of a drum. This increases the friction and slows down the wheel effectively.

The design of the s-cam drum brake allows for high stopping power and reliability, which are crucial for heavier vehicles that require stronger braking forces. Additionally, this braking system is well-suited for conditions where traditional disc brakes may not perform as effectively, particularly under heavy loads or extreme conditions.

In contrast, while disc brakes are also effective, they are more commonly found on passenger vehicles rather than heavy commercial vehicles. Air brakes, typically used in large trucks, refer to the overall brake system that may incorporate s-cam drum brakes at the wheel level. Hydraulic brakes are prevalent in smaller vehicles but are less common in heavy-duty applications where the s-cam drum brake excels.