When a race car isn't handling well, the team depends on the driver to communicate the problem to the crew chief so that adjustments can be made during pit stops. Handling is judged by how well a car gets into and out of the turns. Obviously, the better the car handles, the faster the driver can go.
When a driver reports that his car is tight, it means that the car is not turning well and that traction in the front is poor. This is also known as understeer or pushing.
When a driver says his car is loose, also known as oversteer, it means that the car has poor rear traction, causing the car to fishtail toward the wall.
Using a ratchet to turn a jackscrew during a pit stop, a crewman can add or subtract spring compression that will bring the frame and trailing arm either forward or away from each other. This adjusts the car's weight on each wheel and applies more or less tire pressure when the car goes into a turn. This is what is meant by adding or removing wedge from the car. By taking out (lowering) the wedge, push can be reduced. By increasing (raising) the wedge, the car can be tightened. A full round of wedge means that the crewman will turn the ratchet 360 degrees, although more drastic adjustments may require several rounds, while sometimes only half a round is added or removed.
Loose and tight conditions can also be remedied by adjusting the air pressure in the tires. An increase in air pressure raises the "spring rate" in the tire and changes the vehicle's handling characteristics. If the race vehicle is tight coming off a corner, a driver might request a slight air pressure increase in the right rear tire to loosen it up.