What is the function of the wheel arch of the car's rear fender?
The core function of the car's rear fender and wheel arch (including the inner lining of the wheel arch) is to prevent the splashing of mud, water, and sand caused by the tires, protecting the car's paint finish, chassis components, and the safety of pedestrians, and assisting in noise reduction and aerodynamic optimization.
Core function
Splash-proof protection: Prevents mud, water, stones, and dust thrown out by the rotating tires from damaging the vehicle's paint surface, chassis wiring, suspension ball joints and other critical components, thus preventing rust and damage.
Longer lifespan: Reduces the erosion of corrosive substances (salt water, mud) on metal structures and rubber parts, lowers maintenance frequency, and extends the overall vehicle lifespan.
Noise reduction and silence: Some plush or thick material inner linings can absorb the noise generated by tire rolling and air flow impact, enhancing the interior quietness (especially for luxury models).
Safety and cleanliness: Reduces the obstruction of rear-view visibility by splashing objects or the impact on pedestrians or the rear vehicle, keeping the vehicle body and surrounding environment clean.
Aerodynamic assistance: The properly designed wheel arch inner linings can guide the airflow and reduce turbulence (but poor or improperly installed ones may increase wind resistance and fuel consumption).
Notes for Attention
Not all vehicles come with the standard features: Some models are not equipped with rear fenders at the factory, which is done to optimize the original chassis airflow design to reduce wind resistance and fuel consumption. Installing them requires assessing whether it would disrupt the aerodynamic layout.
Material and Compatibility: High-quality inner linings often use materials such as TPV/modified PP that are resistant to high and low temperatures; they need to be precisely matched according to the wheel spacing and suspension travel of the vehicle to avoid interfering with steering or causing cracking.
Distinguishing Concepts: "Wing arch" refers to the arched structure of the vehicle body above the wheels (including the outer panel, fender, and inner lining); "fender" usually refers to the mud guard hanging at the rear of the vehicle; "inner lining of the wing arch" is the protective plate inside the wing arch, and these three often work together but are located differently.
Cracking of the rear wheel fender mainly occurs due to the combined effects of material aging and brittleness, impact from road debris, concentrated installation stress, or low-temperature hardening.
Core Causes
Natural Aging and Material Defects: Rubber or engineering plastics are exposed to ultraviolet rays, rain, and temperature differences over time, causing molecular chain breakage, resulting in loss of elasticity and hardening and brittleness. This is more pronounced in winter; inferior materials with insufficient anti-aging agents will accelerate this process.
External Impact and Fatigue: Repeated impacts from flying stones and sand during driving, or severe vibrations caused by passing over bumps or potholes， cause physical damage or cumulative fatigue cracks.
Installation and Structural Stress： Over-tightening of the fixing screws， incorrect position of the clamps， or poor fit of the original design can cause the fender to bear abnormal tensile stress when the vehicle shakes， resulting in cracking at the fixing point or weak area.
Handling suggestions
Minor cracks: After cleaning and drying the cracks, use automotive-specific plastic glue/epoxy resin for bonding, and then sand it smooth after curing; for small cracks, plastic welding can also be attempted for repair.
Severe damage/multiple cracks: It is recommended to replace the part directly.
Preventive maintenance： Regularly check the tightness of the fixing clips， and promptly remove stones and sand from the gaps after bad road conditions.
If you are unsure whether the cracks affect the structural safety or cannot judge the degree of damage by yourself， it is recommended to go to a professional repair shop for assessment to prevent splashing mud and water from corroding the car paint or chassis components.
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