What Causes Brake Failure on Rainy Days?
3 Answers
Brake failure on rainy days can be attributed to weather conditions: the slippery road surface reduces friction between the tires and the ground, leading to decreased braking effectiveness. The following are vehicle-related causes: 1. Air in the brake lines: Brake fluid is the medium that transmits force in the braking system. If air enters the brake lines, the brake fluid under high pressure will lose some of its effectiveness, resulting in noticeably weaker maximum braking force. To check for air in the brake lines, turn off the engine and pump the brake pedal several times until it becomes firm. Then, hold the pedal down. If it remains firm, the system is normal. If the pedal slowly sinks, it indicates air in the brake system. 2. Long overdue brake fluid replacement: If brake fluid is not replaced in time, it may contain excessive impurities and moisture, which can impair the transmission of braking force. Therefore, brake fluid should be replaced regularly, and it is advisable to have its moisture content tested at a repair facility if possible.
I often encounter situations where the brakes don't work well in rainy weather, especially during heavy rain. The main reasons include slippery road surfaces and reduced friction between the tires and the ground, which significantly increases braking distance. Rainwater can also wet the brake discs, affecting braking performance, and may even form a water film that causes brake failure. Additionally, if the tire tread is severely worn, the drainage performance is poor, making it easier to skid. When driving in the rain, I have to slow down in advance, maintain a safe distance, and control speed by gently tapping the brakes instead of slamming them. Regular vehicle checks are also important, such as ensuring proper tire pressure and that the brake pads are not worn, which can help prevent sudden issues. When it rains, oil stains on the road mix with rainwater, creating an even more slippery situation, which is another risk factor.
When working in the repair shop, I see many braking issues during rainy days. The reduced tire grip in wet conditions is due to water lowering the road's friction coefficient, and insufficient friction leads to poor braking. The braking system itself is also affected—for example, rainwater entering brake components can cause vapor lock or steam, weakening braking force. Tires are crucial; insufficient tread depth worsens water drainage. Additionally, ABS systems are supposed to help on slippery roads, but vehicles without ABS or older models face higher risks. I recommend driving at lower speeds in the rain and applying gentle, repeated brake presses during emergencies to avoid wheel lockup. Regular maintenance is essential—checking brake fluid and tire condition can eliminate hazards before the rainy season.
