page_title: Vehicle frame
section_title: Ladder frame
hierarchical_section_title: Vehicle frame / Types / Ladder frame
caption_attribution_description: Developed ladder chassis with diagonal cross-bracing and lightening holes
context_page_description: A vehicle frame, also known as its chassis, is the main supporting structure of a motor vehicle to which all other components are attached, comparable to the skeleton of an organism.
  Until the 1930s, virtually every car had a structural frame separate from its body. This construction design is known as body-on-frame. Over time, nearly all passenger cars have migrated to unibody construction, meaning their chassis and bodywork have been integrated into one another.
  Nearly all trucks, buses, and most pickups continue to use a separate frame as their chassis.
context_section_description: Named for its resemblance to a ladder, the ladder frame is one of the simplest and oldest of all designs. It consists of two symmetrical beams, rails, or channels running the length of the vehicle, and several transverse cross-members connecting them. Originally seen on almost all vehicles, the ladder frame was gradually phased out on cars in favor of perimeter frames and unitized body construction. It is now seen mainly on trucks. This design offers good beam resistance because of its continuous rails from front to rear, but poor resistance to torsion or warping if simple, perpendicular cross-members are used. The vehicle's overall height will be greater due to the floor pan sitting above the frame instead of inside it.
caption: Ladder chassis with diagonal cross-bracing and lightening holes
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