Why does the brake feel soft and ineffective after replacing the brake pads?

[StGarrett]

After replacing the brake pads, the brake feeling soft and ineffective is mainly due to the following two reasons: 1. The surface of the brake pads is relatively flat. 2. The contact area with the brake disc is small, resulting in lower braking force. New brake pads require a break-in period, typically around 200 kilometers. Only after this break-in period can the optimal braking performance be achieved. Different issues have different solutions: 1. Severe wear of the brake pads. Some cars are equipped with a brake pad wear warning function. Once the brake pads wear close to the critical value, a warning light will appear on the dashboard. Even without this function, there are raised indicators on both sides of the brake pads, which represent the wear critical value. When the brake pads wear down to these raised indicators, they will contact the brake disc and produce abnormal noises. At this point, the brake pads should be inspected and replaced promptly. 2. Leakage between the master cylinder and the wheel cylinder. The master cylinder internally uses the brake pedal to pressurize the brake fluid, which then transmits the pressure to the wheel cylinders, pushing the brake pads to frictionally engage the brake disc and generate braking force. If there is internal leakage between the master cylinder and the wheel cylinders, the pressure will dissipate internally, causing the brake to feel soft. To resolve this, the internal air should be bled, and the brake lines should be inspected and replaced promptly.

[Alves]

Just changed the brake pads and found the brakes feel soft and ineffective? I've pondered this issue many times. The most common reason is accidentally introducing air into the system during pad replacement, making the hydraulic line feel spongy like a half-empty soda bottle. Also, check the brake fluid – old fluid absorbs moisture, which vaporizes under heat to create bubbles, significantly reducing braking power. New brake pads and old rotors need a few days to bed in properly; initial contact surfaces aren't optimal, so friction naturally falls short. I've also encountered situations where brake caliper pistons don't retract properly, causing partial drag that worsens braking. My advice: drive about 100km after replacement for proper bedding. If issues persist, have a mechanic inspect for fluid leaks or deteriorated brake fluid.

[MacEdward]

A while ago, I experienced a scary situation where my brakes failed right after replacing the brake pads myself, which nearly gave me a cold sweat. An experienced driver told me there are three main points to check: first, whether there's fluid leakage in the brake lines, as insufficient hydraulic pressure naturally leads to weak braking; second, whether air bleeding was incomplete during replacement, as tiny air bubbles in the lines can make the pedal feel like stepping on cotton; third, whether the new brake pads are too smooth, causing poor initial contact with the decade-old brake rotors—just like new shoes needing a break-in period. Another possibility is installing low-quality brake pads with improper metal content that fail under high temperatures. Remember to check the brake fluid reservoir level—if it depletes quickly, return to the shop immediately for inspection. Now, I always allow a three-day break-in period after changing brake pads and never dare to hit the highway right away.

[MaddoxRose]

New brake pads installed but still can't stop? Mostly due to unaddressed basic issues. First, check for air intrusion—air bubbles in the brake system lengthen pedal travel, requiring re-bleeding. Next, inspect brake fluid condition: replace if older than two years or containing over 3% water, as aged fluid vaporizes under high temperatures, reducing braking power. Mismatch between new pads and old rotors is critical—different metal formulations or improper installation angles decrease friction efficiency. Watch for fluid leaks—worn caliper seals or loose fittings can cause pressure loss. The easiest solution? Have technicians scan data streams with diagnostic tools post-installation to verify balanced braking force across all wheels—any deviation warrants wheel removal for re-inspection.