Brake Fade on a Loaded Downhill Grade
You are driving a 4-tonne cargo truck loaded with 3.5 tonnes of rice. The route descends a 6 km mountain road with an average 8% grade. At the 2 km mark, the service brake pedal feels soft and travels closer to the floor; you smell hot brake lining, and the truck’s speed has crept from 40 kph to 55 kph despite steady pedal pressure. The engine brake is operational, but you are in 5th gear. Ambient temperature is 34°C. A sign says “Runaway truck ramp 1.2 km.” Traffic behind is light; oncoming traffic is moderate. The next safe pull-out is 800 m ahead. Your load is not secured against forward shift, and the truck has an 18-tonne GCW rating. You are 1.8 km from the ramp and the pedal is still firm enough to slow the truck slightly.
1. What is happening, and what should you do in the next 10 seconds?
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This is brake fade: continuous service-brake use on an 8% grade has overheated the linings/drums, reducing friction. The soft, long pedal and hot-lining smell confirm heat; speed creep shows braking force is falling.
Immediate actions: release the service brake, downshift progressively from 5th to 4th and then 3rd to bring engine braking into play, switch on hazard lights, and use the engine/exhaust brake. Steer for the 800 m pull-out or the 1.2 km ramp if speed cannot be controlled. Use firm, intermittent brake applications rather than riding the pedal. Avoid a sudden downshift that over-revs the engine; match road speed to gear. Keep steering control and warn traffic behind.
2. Why is coasting in neutral or holding the clutch down dangerous in this situation?
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Coasting in neutral or holding the clutch removes engine braking, so the truck accelerates and relies entirely on already overheated service brakes. That increases fade, pedal travel, and stopping distance. It also reduces driver control because there is no direct engine-to-wheel braking effect and the vehicle can run away on the grade. Staying in gear lets compression braking limit speed and gives a reserve if the service brakes fade further.
3. After you stop safely, what inspections and decisions must you make before continuing?
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Park on level ground, chock the wheels, and let the brakes cool naturally. Inspect lining thickness, glazing, brake fluid level and leaks, drums/discs for heat discoloration, and tires. Do not pour cold water on hot drums-cracking risk. Check load securement because the load may have shifted forward.
If the pedal is still soft, fluid is leaking, or linings are glazed/worn, do not continue; call for service. If components are serviceable, descend in a low gear, use intermittent braking and pull-outs, keep speed well below 40 kph, and report the fade event. A repeated fade means the vehicle must be removed from service.