Body in white

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Body in white (BIW) is the stage in automobile manufacturing in which a car body's frame has been joined together, that is before painting and before the motor, chassis sub-assemblies, or trim (glass, door locks/handles, seats, upholstery, electronics, etc.) have been integrated into the structure. Assembly involves different techniques such as welding (spot, MIG/MAG, or friction stir), riveting, clinching, bonding and laser brazing.

The term derives from manufacturing practices before steel unibody monocoques,^[when?] when automobile bodies were made by outside firms on a separate chassis with an engine, suspension, and bumpers attached.^{[citation needed]} The manufacturers built or purchased wooden bodies (with thin, non-structural metal sheets on the outside) to bolt onto the frame. The bodies were painted white prior to the final color.^{[according to whom?]}

A folk etymology for "body in white" is the appearance of a car body after it is dipped into a white bath of primer (undercoat paint)— despite the primer's actual gray color.^{[citation needed]} BIW could also refer to when car bodywork would be made of timber – all timber products, furniture, etc., are considered to be "in the white" when at the stage of raw timber before finishing or varnishing.^{[original research?]}

In car design, the "body in white"^{[inconsistent]} phase is where the final contours of the car body are worked out, in preparation for the ordering of the expensive production stamping die. Extensive computer simulations of crash-worthiness, manufacturability, and automotive aerodynamics are required before a clay model from the design studio can be converted into a body in white ready for production.^{[citation needed]}

Factories may offer BIW cars to racers, who then may replace up to 90% of the car with aftermarket parts,^[1] and niche manufacturers like Ruf Automobile start their cars with BIWs from other makers.