Different types of Braking Systems Explained by Myles Truck Repair in Lawrenceville, Atlanta, Duluth, and Buford Georgia
Semi trucks have very complex braking systems. There are three specific types of brakes. There are service brakes (air brakes), parking brakes (spring brakes), and the emergency braking system.
Air brakes use pressurized air to activate the braking system. These breaks are used most, during your daily driving. The most common type of brakes used in semi trucks are called S-cam brakes, because the mechanism used to push the shoes against the drums is S shaped. There are also wedge brakes and disc brakes which are less common. Semi trucks with air brakes, manufactured after March 1, 1998, are also equipped with ABS, which keeps the wheels from ceasing up during hard braking.
The parking brake system comprises brakes that are activated by a loss of air pressure. This air pressure loss can occur through an air leak or other emergency or can be controlled manually through the push/pull knob in the cab. Air pressure holds these brakes open during normal driving conditions. They activate when the air pressure can no longer overcome the pressure being exerted by the springs. The spring brakes are used primarily for securing the semi when parked.
The emergency braking system activates the spring brakes when the vehicle loses air pressure in an air brake system. The spring brakes engage engage when the air pressure drops below 20 to 45 psi in the air storage tanks, thus stopping the vehicle. These brakes can sometimes be disengaged by the use of air located in a separate tank (if so equipped) in order to move the vehicle out of a potentially dangerous situation. These brakes can also be applied manually in the event of brake failure in vehicles equipped with a modulating valve. The modulating valve allows the driver to gradually apply the parking or spring brakes through the use of a lever in the cab in an effort to slow the truck down. When parking a semi truck with a modulating valve, the level must be placed in the “fully on” position and locked in place with a locking device.
If you are having any braking issues with your semi truck, Myles Truck Repair in Atlanta, Lawrenceville, Duluth, and Buford would be happy to pinpoint what the problem is and fix it in a timely manner! Call us today at 770-237-3200