What Causes Weak Braking After Replacing Brake Pads?
2 Answers
Newly replaced brake pads may fail to stop the vehicle properly because: the wear levels on both sides of the brake pads differ significantly, leading to uneven braking force. This can cause one side to lock up while the other side hasn't engaged fully, resulting in the car pulling to one side. Braking relies on intense friction between the brake pads and the brake drum. When driving through water, the wheels are almost entirely submerged, leaving a thin layer of water between the brake pads and the drum. This acts like a lubricant, reducing friction and making it difficult to stop the car. Additionally, water trapped inside the drum doesn't dissipate easily. This loss of braking occurs very suddenly. After exiting the water, repeatedly applying the brakes while driving will wipe away the water droplets between the brake pads and drum. The heat generated by friction will also dry them out, quickly restoring the brakes' original sensitivity. This phenomenon rarely occurs in cars with disc brake systems because the brake pads in such systems have a small surface area, and the disc is fully exposed, preventing water retention. Due to centrifugal force from wheel rotation, water on the disc will disperse automatically, ensuring the braking system functions normally. Many compact cars use a front-disc-rear-drum braking setup, which is why some brakes may fail or weaken significantly after driving through water.
I also experienced weak braking right after changing brake pads. Upon checking, I found the issue might be with the brake fluid. If the system isn't properly bled during pad replacement, air can remain trapped, affecting hydraulic pressure transmission. Additionally, new brake pads require some break-in time - their surfaces may initially be unevenly smooth with lower friction coefficients, so unresponsive braking during the first few presses is normal. I remember once testing new pads immediately on the highway, only to find the brakes ineffective, which scared me into rushing back to the shop. Turned out the bleeder screw wasn't tightened properly, causing fluid leakage. My advice: after pad replacement, test at low speeds first, avoid hard braking, and pump the pedal several times to help the system adjust. If braking remains weak, check whether the brake fluid is overdue for replacement or insufficient - both can cause similar issues.
