the roof support on either side
of a car's windshield.
active suspension: an extremely sophisticated, computer controlled
suspension system that uses powered actuators instead of conventional
springs and shock absorbers. The actuators position a car's wheels in the
best possible manner to deal with road disturbances and handling loads.
aerodynamic drag: the drag produced by a moving object as it
displaces the air in its path. Aerodynamic drag is a force usually
measured in pounds; it increases in proportion to the object's frontal
area, its drag coefficient, and the square of its speed.
air dam: a front spoiler mounted beneath the bumper and shaped to
reduce the airflow under the car. Air dams can increase the airflow to
radiators, reduce aerodynamic drag, and/or reduce lift.
anti-dive: a tuned-in front suspension characteristic that converts
braking-induced forces in the suspension links into a vertical force that
tends to lift the body, thereby reducing dive under braking.
anti-lock-braking system: a braking system that senses when any of
the wheels have locked up, or are about to, and automatically reduces the
braking forces to keep the wheels rolling. Commonly called ABS, such a
system can control all four wheels or only two.
anti-roll bar: a suspension element (used at the front, the rear,
or both ends of a car) that reduces body roll by resisting any unequal
vertical motion between the pair of wheels to which it is connected. An
anti-roll bar does not affect suspension stiffness when both wheels are
deflected equally in the same direction. Often incorrectly called a sway
anti-squat: similar to anti-dive, this suspension characteristic
uses acceleration-induced forces in the rear suspension to reduce squat.
apex: the point(s) or region on the line through a corner that
touches the corner's inner radius.
aspect ratio: generally the ratio between two dimensions of an
object. In tire terminology it applies to the unloaded sidewall height of
the tire divided by its overall width. A lower aspect ratio implies a
shorter, wider tire. When used to describe a wing it is the span of the
airfoil (the long dimension perpendicular to the airflow) divided by its
chord (the dimension parallel to the airflow).
axle tramp: A form of wheel hop that occurs on cars with live
axles, caused by the axle repeatedly rotating slightly with the wheels and
then springing back.