Brake systems for trucks

Air Brakes

Trucks use air brakes instead of hydraulic brakes like in passenger cars. The system consists of a compressor, air tank, valves, and brake cylinders.

Spring brakes are an important safety feature. When the air pressure falls below a critical level, the vehicle is braked automatically. This prevents the truck from rolling uncontrollably.

Minimum Air Pressure

• The system must have at least 6.5 bar for normal operation.
• Warning lights and buzzer are activated at around 5.5 bar.
• Stop immediately and troubleshoot if the pressure drops while the engine is running.

Retarder

A retarder is an auxiliary brake that slows down without friction. It comes in two main types:

• Hydraulic retarder brakes via fluid resistance in a turbine.
• Electromagnetic retarder uses a magnetic field to slow the shaft.

The retarder is used on long downhill runs to relieve the main brakes and prevent overheating.

Engine brake and exhaust brake

Engine brake (jake brake) utilizes the engine’s compression resistance to slow down. Exhaust brake closes the exhaust valve and increases resistance further.

• Use engine brake and exhaust brake on downhill runs to maintain a steady speed.
• Combine with retarder for best effect on long slopes.
• These systems do not wear on the brake linings.

Maintenance and inspection

• Check brake pads and drums regularly.
• Make sure the air dryer works to avoid moisture and ice in the system.
• Drain condensate from the air tanks after longer driving in cold weather.

Further Reading

• Read about cargo securing and weight regulations .
• Practice with free theory test for trucks.