air (dirty or clean)
Open cockpit cars are designed and tuned to work well when conditions are not ideal. If a car is travelling around a track by itself (such as in oval track qualifying), the air is undisturbed and is considered clean. However, each car throws off a significant amount of turbulence in its wake, much like the waves and bubbles created by a moving boat. If a car travelling behind another car is affected by this turbulence, the air is considered dirty. Careful attention must be paid to tuning the aerodynamics so that the car works well in both clean and dirty conditions.

air pressure
With the advent of radial tires with stiffer sidewalls, changing air pressure in the tires is used as another setup tool that is akin to adjusting spring rates in the vehicle’s suspension. An increase in air pressure raises the spring rate in the tire itself and changes the vehicle’s handling characteristics.

altered
A drag racing class that uses car bodies with any manner of modification.

apex
The geometric inside center point of a corner. A driver will often use a late apex, turning into the corner a little later than normal in order to straighten out the last part of the corner. This allows the driver to accelerate earlier and harder, gaining maximum speed down the next straight.

apron
The paved (and usually flat) portion of a racetrack that separates the racing surface from the infield. Generally, a concrete wall or steel guardrail separates the apron from the infield.

attenuator
A safety device made of carbon fiber and honeycombed aluminum mounted on the rear of the gearbox. Enhances driver protection by absorbing much of the force of a rear impact.