How NASCAR Wedge Adjustments Work

Suspension in a NASCAR Race Car
This is an example of a typical kind of suspension spring that may be used in NASCAR race cars.
This is an example of a typical kind of suspension spring that may be used in NASCAR race cars.
Jon Ferrey Allsport/­Getty Images

Wedge adjustment simply refers to adjusting the amount of force that bears down on a tire's spring. So before we go any further, we should emphasize how springs are used in a NASCAR race car's suspension system.

­What makes jumping on a bed so much fun? Unlike a hard floor, the springs inside a bed make the most out of the downward force you exert when you jump -- in fact, they give it back to you in upward force, allowing you to jump even higher. You can push down on a floor all you want -- it won't push back. Springs, however, do. The reverse happens when you try to pull the ends of a spring outward -- they'll try to pull back. Springs are such stubborn and resilient things, in fact, that the harder you compress or stretch them, the harder they will push or pull back. In physics, this is called Hooke's Law.

Car engineers are able to take advantage of a spring's unique qualities in a car's suspension system. This system is meant to combat the negative affects of bumps on a road. When a car is moving and encounters a bump, that bump spends energy by transferring some of the car's forward force to upward force. It can also make the tires lose their grip on the road. If you ever got a tire stuck in the mud, you know how important grip is. Although NASCAR racetracks may not have any mud, even the slightest loss of grip can affect a car's performance.

Springs are a great way to absorb the energy that tires encounter with bumps. With a spring at each tire, these suspension systems transfer the energy of the jolting tire to its spring, which pushes back. This keeps the tire in constant contact with the road as the springs continue to push wheels downward.

Even using springs, maintaining grip between the road and the tire can still be difficult when taking a turn at a high speed. This is what happens during NASCAR races. If weight shifts off of a tire during a turn, the tire will lose grip with the road and the driver will have less control of the vehicle. It turns out that the amount of tension on a spring can alter how much of the total weight bears down on a given wheel. When adjusted appropriately, the amount of tension on the individual springs can help attain proper weight distribution and grip during a turn.

­But here's how things get tricky: When you adjust the tension of a spring on one wheel, it can affect the other three wheels in interesting ways. Find out how next.