Those of us who watch Winston Cup and Busch racing on television have many times seen a middle-of-the-pack race car start running with the leaders following a pit stop, or a front-running car start to fall back in the field. The key is whether the crew makes the right handling tweaks during the pit stop.
Crewmen can use a number of methods to adjust a cars handling. These include raising or lowering the track (Panhard) bar, increasing or decreasing crossweight (wedge), adding or taking out spring rubbers, adding or removing tape, and increasing or decreasing air pressure in any of the tires.
Race teams divide the corner of a racetrack into three parts: entry, middle, and coming off the corner. The terms loose and tight are the terms used to describe the reaction of the car. Loose means that the car wants to come around and spin out (rear end going toward the outside wall.) Tight means the car wants to go straight instead of turning.
The late Neil Bonnett best described these conditions when he said, When the car is tight, you get to see the accident. If its loose, you just get to feel it. There are many degrees of tight and loose, but both conditions make the car slower through the turns. When you overhear a driver say, The car wont turn, he is referring to a tight race car.
The driver and the crew chief have to have a good understanding of what each other means to know how drastic an adjustment to make. Going too far with an adjustment will make a tight car loose and vice versa. The best crew chiefs have to almost be able to read their drivers mind.
Track Bar, Spring Rubbers
The track bar runs across the car, holding the rearend housing in the middle of the car. Raising the bar on its attachment on the right framerail will loosen the car. Obviously, lowering the bar would then tighten the car. The track bar is adjusted at the right rear of the car through a hole in the rear window. The crewmember, usually the rear-tire carrier, uses a special wrench that he puts in the hole and turns the bolts on the track-bar adjuster. Raising the track bar is sometimes done to help the car turn in the middle of the corner.
A spring rubber is placed between the coils of a spring to make that spring stiffer. Seldom do you see a rubber being added, as it takes too much time on a pit stop. On the other hand, crews put handles on the rubbers so they can be removed quickly when the car is jacked up. The tire changer removes the rubber. Basically, removing a rubber from the right front softens the spring and will help a pushing or tight condition; removing a rubber from the right rear helps a loose condition. Crew chiefs place these rubbers in the springs to give them flexibility in changing spring rates during the race as the track conditions change.
Wedge
The two previous adjustments are fairly new to stock car racing. Changing crossweight, or wedge, is as old as racing itself.
In a race car, a large bolt runs from the frame to the top of each spring. This bolt holds the car at its given ride height and supports the total spring weight of the car. If you turn one of these bolts down, it will increase weight on not only that tire of the car, but also to the tire diagonal to it (Example, right front and left rear). An asphalt race car is set up with more total weight on the right front and left rear than on the left front and the right rear. This is referred to as the crossweight. It is commonly given as a percentage of total weight.
Winston Cup cars are not allowed to change the front-wedge bolts after the car goes through inspection, so any wedge adjustment must be made in the rear. It would be necessary to raise the hood to adjust the front-wedge bolts anyway. The rear-wedge bolts are adjusted through a hole in the rear window, also by the tire carrier. The hole for the right rear wedge bolt is forward of the hole for the track bar.
Crossweight is added by backing off the right side or cranking down on the left wedge bolt. Adding crossweight tightens and decreasing crossweight loosens the car.
Tape and Tires
At the beginning of a race, crewmen place several strips of duct tape across the front valence of the car. You usually dont see these because they are the same color as the car. The teams would like to run as little opening at the front as possible. In fact, the nose is usually blocked off completely for qualifying. The less air that enters the nose, the more downforce there is on the front end. The amount of opening has to be tempered with the cooling of the engine. During a race, you may see the front-tire carrier pull off a piece of this tape, because the engine is running too hot. This will allow more air to enter the radiator, but it also will take some downforce away from the car and cause the car to become tighter.
In the age of radial tires, the change you hear the most about is air pressure in the race cars tires. Basically, this adjustment has the effect of changing the spring rate on that corner of the car. Each tire in itself acts like a spring; the lower the pressure, the softer the spring. If the car is tight, or pushing, the crew will lower the pressure in the right-front tire. If the car is loose, they will lower the right rear, just as they did with the spring rubbers.
One adjustment a driver can do inside the car is to change the front-to-rear brake ratio by turning a handle. The driver can add rear brake to help a tight race car enter a turn better. Backing off the ratio to the rear may help a car that is loose entering the turn. On big tracks where brakes are not used, you will sometimes see someone spin out entering pit road. This could result from too much rear-brake bias.