Wet Road, Worn Tyre, Late Braking
It is raining steadily and the road surface is wet with a thin film of water. You are riding a motorcycle with a rear tyre at 1.4 mm tread depth (the legal minimum in many jurisdictions is 1.6 mm). You are approaching a bend marked with a 50 km/h advisory sign; you are doing 60 km/h. A car ahead brakes suddenly. You apply both brakes, but the rear wheel locks and steps out slightly. You release and reapply, and stop about two metres short of the car. Your hands are shaking and you notice you have been gripping the bars tightly.
1. Explain why the rear wheel locked and how the wet road and tyre condition contributed.
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- Reduced grip: a thin film of water on the road lowers the coefficient of friction. A worn rear tyre at 1.4 mm has shallow tread, so it clears water poorly and is more prone to losing contact - aquaplaning and sliding are both more likely.
- Braking force vs available grip: the rear wheel carries less load under braking as weight transfers forward. If the rider applies rear brake too hard for the available grip, the wheel locks. On a wet road the lock-up threshold is reached at much lower brake pressure.
- Lock and step-out: a locked rear wheel loses directional stability and can slide sideways; releasing it abruptly can cause a high-side. The rider's quick release-and-reapply was the right instinct but should be smoother.
Key point: the tyre is below the legal minimum and is a direct contributing factor; it should be replaced before riding in the wet. Braking should be progressive, with more emphasis on the front brake while the bike is upright, and reduced overall in the wet.
2. What should the rider do differently on approach, and what does the tight grip on the bars tell you?
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On approach:
- Slow down before the bend, not in it. The 50 km/h sign is advisory for dry conditions; in rain, ride below it.
- Increase following distance - in wet weather, at least double the dry-weather gap.
- Scan further ahead and anticipate the car braking (brake lights, traffic ahead).
- Use smooth, progressive braking while upright, then ease off before turning in.
Tight grip: gripping the bars hard is a sign of tension and reduced feel. It transmits rider inputs to the steering and makes the bike less stable. The rider should relax the grip, use the legs and knees to hold the tank, and keep the arms loose so the bike can move underneath. Tension also slows reaction and increases fatigue.