How to judge whether the car suspension spring needs to be replaced?

1. Body posture change detection
Phenomenon: The vehicle sinks on one side when parked (such as the height difference between the left and right wheel arches is greater than 15mm) or collapses as a whole, and the height of the vehicle body is lower than the original factory calibration value when unloaded.
Detection method: Use a tape measure to measure the vertical distance from the wheel arch to the center of the tire, and compare the coaxial two sides and the original factory data. Press the four corners of the vehicle body and quickly release it. If the number of rebounds is greater than 2 times or the body shakes for more than 3 seconds, it indicates that the damping of the car suspension spring is declining.
Performance: When fully loaded or passing speed bumps, the body touches the bottom, the gap between the tire and the wheel arch disappears, and there is a "clang" abnormal sound.

2. Decreased handling and riding performance
Performance: The turning roll amplitude increases (such as the tilt angle when turning at a speed of 40km/h>12°), and an emergency lane change has a "floating feeling".
Quantitative detection: The ESP system lateral acceleration sensor data can be read through OBD, and the degree of attenuation of the car suspension spring support force can be judged by comparing the parameters of the new car.
Chain reaction failure of the shock absorber system: Spring failure will cause shock absorber oil leakage (single-side oil leakage rate>30ml/month) or top rubber to fall off, causing metal collision noise.
Inspection points: Observe the penetration range of shock absorber oil stains and test whether there is a "thumping" sound on bumpy roads.

3. Abnormal tire wear
Uneven wear characteristics: block or serrated wear on the inside/outside of the tire (depth difference>1.5mm), and the tread is wavy and uneven.
Cause analysis: The collapse of the automobile suspension spring causes the wheel alignment parameters to be inaccurate (such as toe angle deviation>0.5°, camber angle deviation>1°).