Why Can the Car Still Move When the Handbrake Is Engaged?
3 Answers
The reason the car can still move when the handbrake is engaged is that the handbrake locks the rear wheels. For front-wheel-drive vehicles, the car can still drive after the handbrake is pulled, while for rear-wheel-drive vehicles, if the engine's horsepower is sufficiently strong, the rear wheels may still move when the accelerator is pressed despite being locked. Precautions for using the handbrake: 1. Avoid pulling it too tightly to prevent the brake function of the handbrake cable from deteriorating; 2. For automatic transmission vehicles, the handbrake should be engaged before shifting to P; 3. The handbrake cannot replace the foot brake during high-speed driving; 4. Do not forget to engage the handbrake when stuck on a slope. The handbrake, also known as the auxiliary brake, uses a steel cable connected to the rear brake shoes to brake the vehicle. Long-term use of the handbrake can cause the steel cable to undergo plastic deformation, which is irreversible. Prolonged use will reduce its effectiveness and increase the handbrake's travel distance.
When encountering a situation where the vehicle still moves with the handbrake engaged, it's usually related to mechanical wear or adjustment issues. Having driven trucks for nearly thirty years, I've come across similar problems several times. The most common cause is aging and slackening of the handbrake cable—either the internal steel wire is broken or the outer casing is deformed, making it feel tight when pulled but actually failing to press the brake pads firmly. Another possibility is that the rear drum brake shoes are stuck, or the adjusting arm screws are stripped, significantly reducing braking force. Once, when parked empty on a dirt slope, the vehicle slid half a meter even with the handbrake engaged. Upon disassembly, it was found that corrosion of the cable had lengthened its travel. Additionally, oil contamination on brake discs can cause slipping, such as when transmission fluid is spilled onto the discs during maintenance. It's recommended to check the handbrake tension during every service—if the vehicle can still be pushed when the handbrake is engaged at seven clicks, immediate repair is necessary, especially for vehicles frequently driven on mountainous roads.
I can totally relate to this. Last time I parked my car on the slope of a shopping mall's underground garage, I clearly pulled the handbrake five notches with a clicking sound, but when I got out, I noticed the car was still slowly moving. I quickly jumped back into the car and pressed the foot brake, breaking out in a cold sweat. A car-savvy friend told me that nowadays, electronic handbrakes might falsely indicate they're locked, while mechanical handbrakes often suffer from uneven wear of brake shoes or slipping due to water. Especially on rainy days when tires get wet, the friction between rubber and the ground decreases, and relying solely on the handbrake might not be enough. It's best to develop the habit: when parking, press the foot brake while pulling the handbrake, and shift into P before turning off the engine. Also, be aware that wear on the handbrake lever's stopper can cause false engagement, making it seem like it's pulled high when it's not actually in place.
