What is the rear bumper of a car?
The rear bumper of a car is an important safety device installed at the lower part of the car's rear. It is not only a key component of the vehicle's structure, but also plays multiple roles in terms of safety, aesthetics and aerodynamics. Main function
Safety Protection: In the event of a rear-end collision, the rear bumper acts as the first buffer layer, capable of absorbing and distributing the impact force, thereby reducing direct harm to the vehicle structure and occupants. In low-speed collisions (typically below 15 km/h), the internal buffer materials can absorb up to 90% of the impact energy, significantly reducing maintenance costs.
Pedestrian Protection: Modern rear bumpers often use flexible plastic materials, which can effectively reduce the impact on the legs when colliding with pedestrians, meeting international safety standards.
Aerodynamic Optimization: The streamlined rear bumper reduces the air resistance at the vehicle's rear end, improves fuel efficiency, and has a positive impact on the range of electric vehicles.
Integrated Safety Technologies: Today's rear bumpers often integrate reverse radar, reverse camera, sensors, fog lights, reflective plates, and even hidden towing hook interfaces, enhancing driving safety and convenience.
Structural Composition
The rear bumper is typically composed of three layers:
Shell (outer panel): Mainly made of modified polypropylene (PP) or thermoplastic elastomer (TPO), featuring lightweight, corrosion resistance, and easy molding, accounting for the majority of the bumper's weight.
Buffer Material: Located inside the shell, it mostly uses honeycomb foam or crushable resin to absorb collision energy.
Crossbeam: Internally, it consists of 1.2–2.5mm thick galvanized steel plates or aluminum U-shaped channel steel, connected to the vehicle's longitudinal frame through energy-absorbing boxes, serving as the main load-bearing structure, responsible for transferring forces to the frame during medium-high speed collisions.
Position and Appearance
The rear bumper is located at the bottom of the vehicle's rear end, covering the area from the lower edge of the rear taillights to the top of the rear fender, closely connecting with the trunk lid and rear side panels. It is one of the core elements of the vehicle's rear visual design. Sports models often feature diffusers, dual exhaust outlets, and other decorative designs to enhance visual impact.
Material Evolution
Early bumpers were mostly made of metal (such as chrome-plated steel), but modern cars almost exclusively use plastic materials due to their light weight (40%-60% lighter than metal), low cost, easy maintenance, and better compatibility with the vehicle's overall design.
In conclusion, the rear bumper of a car has evolved from a simple "impact barrier" to a comprehensive automotive component that integrates safety protection, lightweight design, aerodynamic optimization, and intelligent integration.
Common Faults of the Rear Bumper
Common symptoms of rear bumper failure include shaking, cracking, detachment, or abnormal sounds. The causes and handling methods depend on the specific symptoms.
Main Fault Types and Handling Methods
Bumper Shaking
Causes: Mostly due to loose connecting screws, deformation of the chassis or suspension system due to collision, abnormal tire weight distribution, or damage to the internal supports of the bumper.
Handling:
First, check and tighten the screws securing the bumper.
If there is no obvious looseness, check the chassis structure at a professional repair shop.
If the internal supports are broken or severely deformed, usually a new part needs to be replaced.
Bumper Cracking or Breaking
Causes: Commonly due to extreme temperature changes (thermal expansion and contraction), long-term exposure to sunlight, cumulative damage from minor collisions, environmental erosion (such as water, salt corrosion of internal metal supports), or product quality defects.
Handling:
Minor Cracks: Can be repaired using professional plastic welding, filling with putty, grinding and painting, with lower costs.
Severe Fragmentation or Large Area Breakage: It is recommended to replace the entire new bumper to ensure structural safety and appearance consistency.
If the vehicle is still within the warranty period and it is confirmed to be a quality issue, contact the manufacturer or 4S store to apply for a free replacement.
Paint Peeling or Chipping
Causes: Mostly due to original factory spraying problems, corrosion by cleaning agents, or water infiltration causing rust and bulging of the underlying layer.
Handling: Partial repainting is possible; If the base layer of the plastic is damaged or has fallen off in large areas, it might be necessary to replace the entire bumper assembly. However, usually, only painting can solve the problem.
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