Vehicle frame

A vehicle's bare ladder frame
Proton Prevé with unibody construction

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.


The main functions of a frame in motor vehicles are:[1]

  1. To support the vehicle's mechanical components and body
  2. To deal with static and dynamic loads, without undue deflection or distortion.
These include:
  • Weight of the body, passengers, and cargo loads.
  • Vertical and torsional twisting transmitted by going over uneven surfaces.
  • Transverse lateral forces caused by road conditions, side wind, and steering the vehicle.
  • Torque from the engine and transmission.
  • Longitudinal tensile forces from starting and acceleration, as well as compression from braking.
  • Sudden impacts from collisions.

Types of frame according to the construction:

  • Ladder type frame
  • X-Type frame
  • Off set frame
  • Off set with cross member frame
  • Perimeter Frame
Other Languages
polski: Rama pojazdu
Simple English: Frame (vehicle)
svenska: Underrede