Air Brakes 101
- By Rachelle Biggs
- Published 11/9/2005
- Driving
- Unrated
The mechanical components involved in providing braking force are: brake chambers, brake drums, brake linings, pushrod, s-cam and slack adjusters.
Brake Chamber Transforms air pressure into mechanical force.
Brake Drums Located on each end of the vehicle’s axles. Wheels are bolted to the drums. The braking mechanism is inside the drum. To stop, the brake shoes are pushed against the inside of the drum.
Brake Linings (or Brake Shoes)
Push Rod A rod, protruding from a brake chamber, which is connected to the arm of a slack adjuster via a clevis pin.
If the pushrod is in, the brakes are released. If the pushrod is out, the brakes are applied.
S-Cam Brakes One of three types of foundation brakes, 80-85% are S-Cam, the others being Wedge or Disc.
Slack Adjuster A lever that connects the brake chamber push rod with the foundation brake camshaft. It provides torque to rotate the brake camshaft when the brake pedal is depressed. It also provides a means of adjusting clearance between brake shoes and drum to compensate for lining wear. There are manual and automatic slack adjusters. Automatics are by far the most common today, but automatic doesn’t necessarily mean no maintenance. You still need to check for proper adjustment.
Brake Chamber Transforms air pressure into mechanical force.
Brake Drums Located on each end of the vehicle’s axles. Wheels are bolted to the drums. The braking mechanism is inside the drum. To stop, the brake shoes are pushed against the inside of the drum.
Brake Linings (or Brake Shoes)
Push Rod A rod, protruding from a brake chamber, which is connected to the arm of a slack adjuster via a clevis pin.
S-Cam Brakes One of three types of foundation brakes, 80-85% are S-Cam, the others being Wedge or Disc.
Slack Adjuster A lever that connects the brake chamber push rod with the foundation brake camshaft. It provides torque to rotate the brake camshaft when the brake pedal is depressed. It also provides a means of adjusting clearance between brake shoes and drum to compensate for lining wear. There are manual and automatic slack adjusters. Automatics are by far the most common today, but automatic doesn’t necessarily mean no maintenance. You still need to check for proper adjustment.