Do cars with ABS systems need to pump the brakes?
2 Answers
With ABS, pumping the brakes is not necessary. ABS, short for Anti-lock Braking System, automatically controls the braking force during vehicle braking to prevent the wheels from locking up. It maintains the wheels in a state of rolling and sliding (with a slip ratio of around 20%) to ensure maximum traction between the tires and the road surface. Working Principle: During braking, ABS quickly determines if a wheel is about to lock up based on signals from each wheel speed sensor. It then closes the normally open input solenoid valve for that wheel to maintain the braking force. If the wheel continues to lock up, the normally closed output solenoid valve opens, allowing brake fluid to flow directly back to the reservoir, rapidly reducing the braking pressure on that wheel and preventing complete lockup. This keeps the braking performance at its optimal point (with a slip ratio S of 20%), ensuring the best braking effect and the highest level of driving safety.
I've been driving for many years, from the old models to the new ones with ABS, and the changes are huge. On slippery roads with old cars, you had to pump the brakes, pressing and releasing alternately to prevent wheel lock-up and skidding. But the ABS system automatically performs this action—it uses sensors to detect wheel speed and rapidly modulates brake hydraulic pressure when lock-up is imminent, eliminating the need for manual pumping. In fact, pumping the brakes can interfere with ABS operation, increasing stopping distance by 10% to 20% and compromising safety. Remember, in emergencies, stomp the brake pedal firmly and hold it down—the pedal vibration during ABS activation is normal, so never ease off due to the pulsing. ABS's greatest benefit is preventing lock-up while maintaining steering control, a life-saving feature that shouldn't be undermined by pumping the brakes.
