g force
The inertial force exerted upon drivers as the car changes direction. One G is equal to the force of gravity. Inertia causes a moving object to try and keep the same speed and direction of travel. Any change in direction creates some amount of G Force. There are six directions of G Force: left/right, front/back and up/down. High-speed corners exert more G force on drivers than do very slow corners due to the additional grip provided by downforce as speeds increase, but braking, acceleration and rises or drops in the pavement also create Gs.

gasser
A drag racer that runs on gasoline instead of nitromethane and alcohol, such as a Pro Stock car.

grid
The arrangement of cars in the starting lineup; at the Indy 500, the grid is made up off 11 rows with three cars per row.

grip
How well the tires maintain traction through contact with the racing surface.

groove
The fastest route through a corner or around the entire track, also referred to as the line. When drivers follow the same line around the track, the build-up of rubber from their tires indicates where the groove is. A high groove takes a car closer to the outside wall for most of a lap, while a low groove takes a car closer to the apron than the outside wall. Road racers use the term line. Drivers search for a fast groove, and that has been known to change depending on track and weather conditions.

ground effects
In airplanes, this refers to a cushion of air that builds up as a plane nears the ground. In Formula One and Champ racecars, this refers to artificially generated low-pressure areas underneath the car that help it adhere to the ground. This is done by tunnels on each side of the bottom of the car, which start off small near the front and gradually get bigger towards the rear, creating a vacuum as the car moves forward using the ground as the fourth side of the tunnel.