What Causes Vibration When Lightly Braking but Not When Braking Hard?
2 Answers
The reasons for vibration when lightly braking but not when braking hard are: 1. Uneven brake disc surface with excessive radial runout: During braking, the contact between the brake pads and the brake disc is uneven, causing fluctuating braking force and resulting in vehicle vibration, which is usually noticeable during light braking; 2. Significant deviation in wheel alignment data; 3. Excessive or insufficient tire pressure: Higher tire pressure causes more severe vibration at higher speeds, while low tire pressure may lead to noticeable vehicle drift; 4. Abnormal tire wear. The car's brake pedal is located below the steering wheel. Pressing the brake pedal activates the brake linkage, which applies pressure to the brake shoes on the brake drum, clamping the brake rotor and causing the car to slow down or stop.
I've encountered this situation many times. Light braking causes shaking while hard braking feels stable, which is often caused by uneven brake disc surfaces. If the brake disc is warped or worn unevenly, light braking applies less pressure, causing friction-induced vibrations; hard braking applies more force, pressing the system tighter, making it less prone to shaking. Common causes include frequent braking while driving leading to disc overheating and warping, or dirt buildup on the disc. I recommend checking the brake disc's thickness and flatness with a micrometer to see if it's below standard - replace it if too thin. If left unfixed, light-braking vibrations may affect control precision, especially increasing skid risks during rain or high-speed driving. For routine maintenance, have the brake system fully inspected every 20,000 km to prevent minor issues becoming major repairs. Replacing with a new disc solves the problem - it's inexpensive but much safer.
