What is a "wedge"?
Unfortunately, its an about.com site and you have to wade through a bunch.
"Wedge is a term that racers have used for years to refer to the amount of weight between the right-front and left-rear wheels," said McGee. "Another slang term for wedge is cross-sway or diagonal. The total weight between the right-front and left-rear tires of the cars is usually a smaller percentage than the carrier between the right-rear and left-front tires. That’s what we call running a car ‘de-wedged’. There’s usually about 45-48 percent of the total weight between the right-front and left-rear tires," says McGee.
If you’ve watched NASCAR racing for any length of time at all, you’ve undoubtedly heard the word wedge thrown around quite a bit. You normally hear a driver or crew chief talking about putting a round of wedge in or taking out a round to free or tighten up the car. But what does that really mean? How much of an effect can it have on the handling of a race car? Stock Car Racing magazine has picked the brains of a couple of really good crew chiefs in the Winston Cup garage, Royce McGee, head wrench for Mike Skinner’s #31 Lowes Home Improvement Chevrolet and Lee McCall, crew chief for Sterling Marlins #40 Silver Bullet Dodge.
"Wedge is a term that racers have used for years to refer to the amount of weight between the right-front and left-rear wheels," said McGee. "Another slang term for wedge is cross-sway or diagonal. The total weight between the right-front and left-rear tires of the cars is usually a smaller percentage than the carrier between the right-rear and left-front tires. That’s what we call running a car ‘de-wedged’. There’s usually about 45-48 percent of the total weight between the right-front and left-rear tires," says McGee.
Simply put, wedge adjustments make the car turn into the corners either looser or tighter.
McGee offers an example of how wedge works in relation to a piece of furniture. "If you take a table on a level floor and shorten the right-front and the left-rear legs 1/4-inch, the other two legs will carry more weight. If you then adjust those two legs by adding a 1/8-inch shim underneath them, that table will rock less," said McGee.
Drivers let the crew chiefs know how the car is handling and what might need to be done to make it better. Oftentimes the solution is a quick wedge adjustment.
"If the driver says that the car is loose in the gas exiting the corner, we’ll put the wedge wrench in a jack bolt in the left-rear window. When you screw down on that left-rear spring, it puts pressure on it and tightens up the car in the gas. If the car is too tight, we go to the right side of the car with the wedge wrench and make the adjustment there. The wedge adjustment changes the load that the springs carry," said McGee.
Wedge adjustments are usually made in half and full turn increments during pit stops. For example, if a driver calls in complaining that the car is tight getting into the corners, the following steps are how the crew would actually loosen the car up during a pit stop. The right-side tire carrier usually makes the actual adjustment after he has given the tire changer the tire. As the right rear tire guy is bolting on the tire, the tire carrier sticks the wedge wrench into the jack bolt located on the top side of the rear window and makes a half or full turn (clockwise) which will loosen the car up. With this adjustment the driver should be able to get into the corners better, which in turn allows him to get on the gas sooner in the corners and turn faster lap times.
Just one turn of a wedge wrench can help a driver go from chasing his car all over the track to charging to the front of the pack.