Brake Pads and Rotor Wear

Excessive wear of brake pads leads to a significant decrease in friction coefficient. Data from a large domestic logistics fleet in 2025 shows that vehicles that did not replace brake pads according to the specified mileage had their emergency braking distance extended by an average of over 15%. When brake pads produce metallic friction sounds, it indicates that wear is near the limit and immediate replacement is required.

Master Cylinder and Wheel Cylinder Failures

Aging piston seals in the brake master cylinder can cause internal leakage, leading to insufficient hydraulic pressure. In a recall initiated by a European brand in 2025, a total of 120,000 vehicles were recalled due to master cylinder seal defects that caused longer brake pedal travel, with a recall rate of 0.8%.

Sticking wheel cylinder pistons or damaged rubber seals can directly affect braking force transmission. The latest repair cases show that wheel cylinder failures can reduce single-wheel braking force by 25%-30%.

Vacuum Booster Pump Failures

Vacuum booster pump failure significantly increases pedal force. Data from the Domestic Market Regulatory Administration's Defective Product Management Center in 2025 shows that complaints involving electric vacuum pumps increased by 18% year-on-year, mainly focusing on circuit reliability in new-generation new energy vehicles.

Insufficient Brake Fluid Pressure

Insufficient brake fluid, ruptured brake lines, or leaking connections are common causes. The revised "Motor Vehicle Brake Fluid Usage Specifications" in 2025 mandate that brake fluid must be replaced when water content exceeds 3%, an increase of 1% from the previous standard.

Air Brake System Leaks

For vehicles with air brakes, insufficient compressor supply or storage tank leaks can lead to low air pressure. A technical bulletin released by a heavy truck brand in 2025 pointed out that when system pressure falls below 6.5 bar, braking distance begins to significantly increase.

Damaged brake lines can directly cause a sudden drop in air pressure. The Shanghai-Kunming Expressway accident investigation report in 2025 showed that brake air lines punctured by road debris were the main cause of vehicle loss of control.

Excessive Brake Pedal Free Play

Excessive pedal free play or brake clearance beyond standards can cause delayed brake response. The "Commercial Vehicle Brake System Maintenance and Inspection Technical Specifications" effective in 2025 requires that the clearance between brake drums and friction linings must be controlled within the range of 0.3-0.5mm.

Lack of Brake System Maintenance

Long-term failure to replace brake fluid can lead to fluid absorption and decreased boiling point. The 2025 industry test report pointed out that brake fluid used for more than two years has an average water content close to 4%, significantly increasing the risk of vaporization.

Heat Fade Caused by High Temperatures

High temperatures reduce the friction coefficient between brake pads and rotors. Summer field test data from 2025 shows that when brake rotor temperature rises from 25°C to 450°C, average braking force decreases by approximately 30%.

Long Downhill Operating Conditions

Frequent braking causes system overheating, exacerbating heat fade. The 2025 Sichuan-Tibet Highway Freight Safety Report pointed out that on continuous downhill sections, proper use of engine auxiliary braking can reduce the main brake system load by over 50%.

ABS System Failures

ABS sensor or control unit failures can affect anti-lock function. In a recall case by a German brand in 2025, 80,000 vehicles were recalled globally due to ABS sensor seal defects causing malfunctions.

Brake System Circuit Failures

Short circuits or open circuits can cause abnormal signal transmission. Domestic new energy vehicle failure statistics from 2025 show that complaints about circuit issues related to brake systems increased by 22% year-on-year, with wiring harness protection and interface reliability becoming focal points of concern.