Bumper (automobile)

A bumper is a structure attached or integrated to the front and rear of an automobile to absorb impact in a minor collision, ideally protecting occupants and minimizing repair costs. Invented by Briton Frederick Simms in 1901, bumpers ideally minimize height mismatches between vehicles and protect pedestrians from injury. Rigid bumpers transmit impact forces both to vehicle occupants and pedestrians; hence numerous regulatory measures have been enacted to reduce the risk to both, at the expense, however, of increasing vehicle repair costs.

Bumpers were at first just rigid metal bars. On the 1968 Pontiac GTO, General Motors brought forth an "Endura" body-colored plastic front bumper designed to absorb low-speed impact without permanent deformation. It appeared in a television commercial where John DeLorean hit the new car with a sledgehammer and no damage resulted. Similar elastomeric bumpers were available on the front and rear of the 1970-'71 Plymouth Barracuda, and in 1971, Renault introduced a plastic bumper (sheet moulding compound) on the Renault 5.

Current design practice is for the bumper structure on modern automobiles to consist of a plastic cover over a reinforcement bar made of steel, aluminum, fiberglass composite, or plastic. Bumpers of most modern automobiles have been made of a combination of polycarbonate (PC) and Acrylonitrile butadiene styrene (ABS) called PC/ABS.

A bumper valance or "valance panel" is a trim piece located in the lower part of the front or rear bumper. Bumper valances are intended to improve aerodynamic efficiency of the vehicle by directing airflow in the same way that an air dam does. Bumper valances may also include the airflow lip at the bottom. However, in many cases valance panel plays a decorative role by covering a lower part of the radiator in the front of the vehicle or concealing the gap between dual exhaust pipes in the rear.

Bumpers offer protection to other vehicle components by dissipating the kinetic energy generated by an impact. This energy is a function of vehicle mass and velocity squared. The kinetic energy is equal to 1/2 the product of the mass and the square of the speed. In formula form:

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