What is Car frame? Definition, types and repair cost

A car frame, also commonly referred to by its chassis is the principal support structure of the motor vehicle, to which the other parts are fixed, similar to the skeleton of an organism.

In the 1930s, nearly every vehicle was equipped with a structural frame that was that was separate from the body. This design of construction is referred to as body-on-frame. In the 1960s, the unibody design in passenger automobiles had become more popular and the trend towards unibody passenger cars grew through the decades that followed.

Functions Of Car Frame

The primary purposes of a car frame within the vehicle include:

  • To help support the vehicle’s mechanic components as well as the body
  • To handle dynamic and static loads without distortion or excessive deflection.

They include:

  • The weight of the body the passengers, the body, as well as cargo load.
  • Twirling that is vertical and torsional caused by the uneven surfaces.
  • The transverse lateral forces are caused by the road, side wind and steering the vehicle.
  • The engine produces torque and the transmission.
  • Tensile force at longitudinal lengths from the beginning and acceleration, aswell in compression from brakes.

Types Of Car Frames

  • Ladder frame.
  • Backbone tube.
  • X-frame.
  • Perimeter frame.
  • Platform frame.
  • Subframe.

Ladder frame

It is named for its resemblance to an a ladder it is among the oldest, most simple and most often used under-body frame designs that are separate from the chassis. It is composed of two beams that are symmetrical or rails that run along across the length of the vehicle and connected by a number of cross-members that are transverse.

Originally found on all cars The ladder car frame was gradually removed from cars to be replaced by perimeter frames and body unitized construction. It is currently seen on trucks with large dimensions.

Backbone Tube

The backbone-chassis is one of the types of automobile construction that includes a chassis that is comparable to the body-on-frame model. Instead of a flat, ladder-like design with two parallel frame-rails running along the length of the frame it is made up of a central tubular backbone that is strong and durable (usually with a rectangular cross-section) which houses the powertrain and connects the rear and front suspension attachments.

types of car frame

Although the backbone is usually pulled upwards, and usually above, the car’s floor however, the body is set on top of (sometimes even straddling) the backbone from below.


This was the style that was used on the large American models made by General Motors in the late 1950s and 1960s where the rails that ran close to the engine appeared to cross the compartment for passengers, with each reaching the opposite end of the cross member located at the rearmost point of the car.

It was specifically selected to reduce their overall size of vehicles, despite the increase in the dimensions of the propeller shaft and propeller shafts since each row needed to be able to cover frame rails as well.

Different models had the differential positioned not via the standard bar between frame and axle instead, but rather via a ball joint on top of the differential, which was connected to an socket that was hinged to a cross-member within the frame.

Perimeter Frame

Similar as a ladder frame but the middle portions frames rails rest outside of the rear and front rails. They run around the footwells of the passenger, which are inside the rocker and sill panel. This allows the floor-pan to be raised, specifically the footwells for passengers, which lowered the seating height of passengers and, consequently, reducing the roof line as well as the overall height of the vehicle, and also the center of gravity, thereby improving the handling and road stability of passenger vehicles.

car frame

This was the most popular style for cars with a body-on-frame throughout the United States, but not throughout the globe until popularity of the unibody grew. For example, Hudson introduced this construction on their 3rd generation Commodore models in 1948. The frame design was able to accommodate regular model changes and also lower-priced cars, which were that were introduced in the 1950s, to boost sales, but without the expense of structural modifications.

Platform Frame

This is a modification to the perimeter frame, or the backbone frame, where the floor of the passenger compartment as well as the floor in the luggage compartment are incorporated into the frame as load-bearing components, to increase durability and strength. The sheet metal used join the parts must be formed with hollows and ridges to increase its durability.

Platform chassis were utilized on a number of popular European automobiles, including those of Volkswagen Beetle, where it was known as “body-on-pan” construction. Another German model can be found in that of the Mercedes-Benz “Ponton” cars of the 1950s and 1960s where it was known as”frame floor” in advertisements “frame floor” in English-language ads.


Within an (tubular) frame chassis the engine, suspension as well as body panel are linked to the skeletal frame in three dimensions made composed of tubes. The body panels serve none of the structural functions. To ensure maximum rigidity and decrease load, the structure often makes the most use of triangles and all forces that are applied to each strut is either compressive or tensile, not bending, which means they are as slim as is possible.

The first real spaceframe chassis were developed during the 30s and 40s of Buckminster Fuller and William Bushnell Stout (the Dymaxion and the Stout Scarab) who understood the idea of a true spaceframe, whether from the design of aircraft or architecture.

Car Frame Damage Repair Costs

The reality is that there’s no defined range of car frame repair cost. It is all dependent on the extent and extent of damage.

Consider a damaged rear quarter panel, for example. If it’s as easy as removing the scratch the repair cost could be between $500 and $1,000.

If the damage is serious the repair could need to have entire sections replaced. This involves taking off old as well as welding onto the new. Industrial machines are utilized to stretch your vehicle in its new size.

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