What is the function of the front lower arm of a car?
The front lower arm of a car is a key component of the suspension system, primarily functioning to support the vehicle's weight, buffer road vibrations, and control the movement trajectory of the wheels. Its specific functions include:
- Support and load-bearing: It bears 30%-40% of the vehicle's weight, transmits longitudinal forces during braking and acceleration, and ensures a stable connection between the wheels and the vehicle body.
- Shock absorption and vibration reduction: Through rubber bushings, it absorbs approximately 80% of the high-frequency vibrations from the road, reducing the jolting sensation inside the vehicle and enhancing comfort.
- Guidance and positioning: It controls the up-and-down movement of the wheels and the steering angle (vertical 20°, horizontal 15°), maintaining the tire contact area and preventing steering blur or high-speed drift.
The cracking of the rubber sleeve on the front lower arm of the car has an impact on safety and may lead to abnormal tire oscillation, poor steering flexibility, and a decline in handling performance, increasing the risk of accidents. Therefore, it is necessary to repair and replace it promptly.
The specific manifestations of the impact on safety:
- Reduced driving stability: The cracked rubber sleeve causes the wheel alignment to shift, making the vehicle prone to veering, side-slip, or shaking of the steering wheel, especially in curves or at high speeds, significantly increasing the risk of loss of control.
- Abnormal tire wear and risk of tire blowout: The failure of the rubber sleeve leads to tire oscillation (commonly known as "tire eating"), uneven wear shortens the tire's lifespan, and in extreme cases, it may cause a loss of grip balance and result in a tire blowout.
- Degradation of handling performance: Steering becomes heavy and inflexible, the shock absorption effect weakens, and there is a noticeable abnormal noise from the chassis during road bumps, and delayed response during emergency braking or obstacle avoidance.
Potential risks and causes:
- The core reason: The rubber sleeve, as a buffering component, cracks and fails to absorb road vibrations and fix the lower arm, causing the suspension system to be unbalanced in force.
- Chain reaction: If not repaired in time, it will accelerate the damage of components such as the ball joint and shock absorber, increasing the repair cost.
- Handling suggestions:
- Immediate repair: If cracks or abnormalities are detected, it is necessary to go to a 4S store or professional repair point for inspection as soon as possible. After replacing the rubber sleeve, a four-wheel alignment must be performed to restore the wheel parameters.
Preventive measures:
- Regular inspection of the chassis rubber sleeve condition (especially for older vehicles) to avoid intense driving or overloading, which can delay aging.
Whether the replacement of the lower arm of a car is considered a major repair depends on the cause of the damage and the complexity of the repair. Generally, it refers to the disassembly and repair of core components such as the engine and transmission, or major, complex structural modifications.
Judgment criteria:
In automotive maintenance, "major repair" usually refers to the disassembly and repair of core components such as the engine and transmission, or major, complex structural modifications. The replacement of the lower arm (also known as the control arm) is a component of the suspension system. Whether it is considered a major repair mainly depends on:
- Scope of repair and complexity: If only the lower arm is replaced (for example, due to aging of the rubber sleeve), it is considered routine maintenance or minor repair and does not count as a major repair.
- Cause of damage and associated injuries: If the lower arm is severely deformed or broken due to a serious accident and involves the overall adjustment of the suspension system, replacement of multiple components, and even the repair of the vehicle's structure, the repair work is complex and may be considered a major repair. Notes for Attention
When conducting a used car valuation or insurance claims processing, simply replacing the tie rod usually does not classify the vehicle as a "major repair vehicle" or a "vehicle involved in a major accident". However, if the replacement occurred due to an accident and the maintenance records indicate extensive repairs to the suspension system, it may affect the determination of the vehicle's value.
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