Pillar (car)

Car pillars are vertical or inclined components An alphabetical convention for designating a car's pillars has developed over time, used variously by the automotive press in describing and reviewing vehicles, insurance companies in identifying damaged components, and first-responder rescue teams to facilitate communication, as when using the jaws of life to cut their way into a wreck. The letters A, B, C, and D are used (in upper case): • The A-pillar is the forward-most pillar on a vehicle, supporting its roof at each corner of the windshield. • The B-pillar is located between a vehicle's front and rear side glass, where it serves as a structural support of its roof. • The C-pillar is the rearmost on two- and four-door sedans and hatchbacks. • The D-pillar is the rearmost pillar on larger four-door vehicles such as station wagons and full-sized SUVs. Posts for quarter windows (a smaller typically opening window on older vehicles between the front door window and windshield, and sometimes found in the rear, usually fixed) are not considered roof pillars. ==Design==

Body pillars are critical in providing strength to an automobile body. As the most costly body components to develop or re-tool, a vehicle's roof and door design are a major factor in meeting safety and crash standards. Before safety standards, pillars were typically thin. The design of body pillars has changed with regulations that provide roof crush protection. Standards in the United States were introduced in phases starting in 2009 that require enclosed passenger cars to be able to support from 1.5-times to 3.0-times the vehicle's unloaded weight on its roof while maintaining headroom (survival space) for occupants. This has meant designing thicker roof pillars that not only provide sufficient strength, but that also incorporate padding and accommodate airbags.) is typically a closed steel structure welded at the bottom to the car's rocker panel and floorpan, as well as on the top to the roof rail or panel. This pillar provides structural support for the vehicle's roof panel and is designed for latching the front door and mounting the hinges for the rear doors. B-pillars also exist as integral elements of an automobile unibody on two-door sedans and hatchbacks, separating the front door from either fixed or movable glass of the second row of seating. Additional doors beyond four, such as on limousines, will create corresponding B-pillars, numbered by order B1, B2, etc.. Closed vehicles without a B-pillar are widely called hardtops and have been available in two- or four-door body styles, in sedan, coupe, and station wagon versions. Designs without a "B" pillar for roof support behind the front doors and rear side windows offer increased occupant visibility, while in turn requiring underbody strengthening to maintain structural rigidity. The need for stronger roof structures meant replacing the pillar-less designs with a rigid B-pillar such as the two-door AMC Matador line. To continue capitalizing on the popularity of the design, General Motors attempted to broaden the definition of "hardtop" during the early 1970s to include models with a B-pillar, with the false rationale, "up to then, everybody thought a hardtop was a car without a center pillar." The "Colonnade" mid-sized General Motors models were so named because of their pillared structure designed to meet new rollover protection standards, but marketers attempted to promote them as if they were true hardtops. By the late 1970s (1978 being the last year of pillarless hardtop cars in the U.S. domestic market), the full-size Chrysler Newport and New Yorker were the last designs with opening front and rear side windows and no B-pillar. The C-pillar is the rearmost on two- and four-door sedans and hatchbacks, and has served as an opportunity for automobile designers "to introduce a little 'design flair' to what would otherwise be a fairly nondescript side view." ==See also==