What are the installation components of the side beams of a car body?
The main components installed on the side beams of the car body are the floor beams, door impact beams, and side skirts. Each of them has a different function.
Floor beam: Located below the front and rear doors, it is the core load-bearing and protective structure of the car body. It mainly enhances the rigidity of the car body and disperses and absorbs impact energy during a side collision.
Door impact beam (side door impact rod): Installed inside the door, it is a steel or aluminum structural component used to strengthen the vehicle's side structure and increase the resistance to side impacts.
Side skirt: Installed below the door on both sides of the car body, it belongs to the car body aerodynamic kit. It mainly optimizes the aerodynamic performance and can also resist scratches.
In addition, the side beam frame will also install pedals, the body, the steering gear, the suspension assembly and its brackets, etc.
The core function of the car body side beams (generally referring to the floor beam, which runs through the front and rear doors, and also including the side door impact beam installed inside the door) is: to provide structural support for the car body and absorb and disperse impact forces during a side collision, protecting the occupants inside. It is also the installation foundation for many chassis components.
Main functions
Structural support: The side beam, together with the roof longitudinal beam and the floor beam, forms the car body frame, enhancing the overall rigidity and stability.
Impact energy absorption: During a side collision, it absorbs and disperses impact energy, preventing the door from denting inward and protecting the occupants' torso and internal organs.
Installation foundation for components: Many chassis components (such as the suspension system, braking system, etc.) are fixed near the side beam, and the strength of the side beam directly affects the overall performance of the vehicle.
The two types of "side beams" should be distinguished.
Floor beam (metal beam running through the front and rear doors): It mainly bears the rigidity of the car body and is the force transmission path during a collision. Do not step on it frequently to avoid deformation.
Side door impact beam (steel/aluminum beam hidden inside the door): It is specifically designed to deal with side collisions. It is usually in tubular or cap shape (U-shaped, M-shaped), made of high-strength steel or hot-formed steel.
The installation components of the car body side beams (such as the bottom beam/door frame beam) and the components connected to them (such as the beam， sub-frame， rubber sleeve， bolts， etc.) that have faults usually refer to deformation， rust， cracks or loosening of the side beam and the components connected to it (such as the beam， sub-frame， rubber sleeve， bolts， etc.). This will directly affect the rigidity and driving stability of the vehicle and requires prompt inspection and repair.
Common fault causes and manifestations
Deformation and collision： Impact， scraping or bottoming out are the most common causes of deformation of the side beam. Long-term overloading may also cause the side beam to deform under pressure.
Rust and aging： Long-term driving in humid or salt-alkali areas， the side beam and its installation points are prone to rust and perforation， affecting the structural strength.
Installation hole damage： If the installation holes of the side beam or the beam (sub-frame) are cracked， deformed or have thread slippage due to rust or impact， it will cause the connection of the components to loosen.
Rubber sleeve aging and cracking： The rubber sleeve (rubber sleeve) at the connection point ages and weakens the buffering effect， causing abnormal noise and vibration.
Typical fault symptoms
Driving abnormal noise： When passing over speed bumps or potholes， there is a continuous "clunk" "grating" sound or friction sound from the rubber sleeve.
Stability deterioration： The vehicle shakes， floats， veers off the straight line when driving， and the steering has fine vibrations or becomes heavy.
Abnormal tire wear： The four-wheel alignment parameters change， causing abnormal wear on the inner or outer side of the tires.
Dullness of the chassis： During driving， it feels that the chassis is overall loose， especially more obvious on bumpy roads.
If the vehicle has symptoms such as the above after a collision or bottoming out， even if the appearance seems not serious， it is recommended to lift the vehicle with a lift and check the side beam and beam as soon as possible， and do not just repair the exterior components.
Treatment methods and repair suggestions
Mild deformation： If the side beam is only slightly deformed， it can be restored to its original state by stretching； but if there are cracks or large folds， it is necessary to cut the damaged part and replace the new part， and use gas protection welding or resistance spot welding to ensure strength and rust prevention.
Severe damage - direct replacement: When the deformation of the exceeds 2mm, the installation holes are damaged, there are irreparable cracks or rusted holes, it is not recommended to attempt to correct or weld. Instead, the original factory parts that meet the OE standards should be replaced directly.
Rubber sleeve damage - separate replacement： The rubber sleeve of the can usually be purchased and replaced separately (the price is not expensive)， but there are specific requirements for the installation angle and pressing method. It is best to use special tools for pressing to avoid damage caused by hammering.
Post-repair inspection： After replacement or repair， a four-wheel alignment should be performed again， and the suspension system， bolt torque， etc. should be checked to ensure that the parameters meet the original factory standards.
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