Winter descent with fading brakes
You are descending a long mountain pass in winter. The road is clear but damp and the temperature is −2 °C, so shaded sections may be icy. The descent is about 6 km with gradients up to 9%. You are driving a fully loaded estate car with four adults and luggage, on winter tyres. The posted limit is 70 km/h. About 2 km into the descent you notice the brake pedal feels longer and softer than at the start, and you can smell a hot, acrid odour. Your speed has crept from 60 km/h to 75 km/h despite steady pressure on the pedal. There is a lay-by 300 m ahead on the right.
1. Diagnose what is happening and decide what to do in the next 300 m.
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Diagnosis: brake fade from overheating. The symptoms together are characteristic - a long, soft pedal (fluid boiling or pads overheating), an acrid smell (hot friction material), and speed rising despite constant pedal pressure (reduced friction). A fully loaded car on a 9% descent makes it worse because the brakes are absorbing the whole energy of the descent.
Next 300 m:
- Stop in the lay-by. Do not 'push on to the bottom' - fade gets worse, not better, and can progress to complete loss of braking.
- Use engine braking now. Select a lower gear so the engine holds the car back; on a long descent the brakes should be used in short, firm applications, not ridden continuously.
- Do not ride the pedal on the way to the lay-by - brake firmly for a few seconds, then release and let them cool.
- Warn following traffic with hazard lights if your speed drops sharply.
- In the lay-by: stop, apply the handbrake, let the brakes cool. Do not pour water on hot discs - they can warp or crack. Check the brake fluid level and look for leaks; if the pedal is still soft after cooling, the car should not continue the descent.
2. After 20 minutes the pedal feels firmer. You must still complete the descent. Explain how you would drive it, including speed choice and gear use.
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Drive the descent on the engine, not the brakes.
- Gear: select a low gear (second, or third if the car is heavy and the gradient eases) so that engine braking holds the car near your target speed without continuous pedal use. In an automatic, use the manual mode or low range.
- Speed: well below the 70 km/h limit - around 40–50 km/h on the steepest 9% sections, slower on shaded bends where ice is possible. The limit is a maximum for ideal conditions, not a target.
- Braking technique: short, firm applications to shed speed before a bend, then release. Continuous light pressure is what caused the fade.
- Ice awareness: at −2 °C, shaded sections and bridge decks can be icy even when the sunny road is damp. Ease off before shaded bends, avoid sudden steering or braking on them, and increase the gap to the vehicle ahead well beyond the normal 2 seconds.
- Watch for a repeat: if the pedal goes long again, stop at the next safe place rather than continuing.
3. A car begins tailgating you closely on the steep section. What do you do, and what do you not do?
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Do:
- Maintain your own safe speed - do not speed up to 'get away' from the tailgater. On a 9% descent, speeding up means more brake energy and a greater chance of losing control.
- Increase your own gap to the vehicle in front so that you can brake gently and early, giving the tailgater more time to react.
- Signal your intentions early and, if there is a safe lay-by or wide section, pull over and let them pass. Removing the tailgater removes the risk of being shunted.
- Keep brake lights meaningful - a brief touch of the brakes warns them you are slowing, but do not brake-check.
Do not: brake sharply to punish them (on a damp, possibly icy descent this can cause a loss of control or a rear-end collision in which you are the one hit); do not accelerate beyond your safe descent speed; do not wave them past on a blind bend.