Getting more power from an engine is something all racers are familiar with. Getting that power to the ground, however, is a science that few racers really understand. For those of you just starting out in drag racing, we’ve put together a basic overview of how chassis and suspension systems are affected by sudden acceleration. The Chassis People™at Competition Engineering want you to understand the relationship between engine power and the chassis, suspension and driveline systems of your car. By doing so, you will be in a better position to select equipment that allows you to hook up and lower ET’s! Without the right chassis and suspension setup, all the horsepower in the world will only go up in tire smoke! As you’re trying to understandhow modifications to the chassis and suspension systems improve traction, it helps to keep one thing in mind. Power produced by your engine must take a direct path to “planting” the tires and “launching” your car forward. Any power that gets absorbed by the chassis and suspension is power that can’t be used to get you to the finish line as quickly as possible. There’s a basic law of physics thatstates “for every action there is an equal and opposite reaction.” Relating this principle to a game of billiards is relatively easy. But applying it to chassis and suspension systems on a drag race car is more complex. When trying to understand how chassis and suspension setups affect traction, keep the “action/reaction” concept in mind. It will make things much easier to understand. While racecars are designed for racing, street cars are designed primarily for carrying passengers safely and comfortably. From the factory, passenger cars are not equipped to handle high rpm launches from a standing start. This instant release of power places great strain on stock suspension systems and usually results in unwanted wheel hop, tire spin and parts breakage. Controlling this unwanted reactionis the job of a traction device, which limits the rotation of the rear axle housing and transfers forces to the track surface. For example, the installation of traction bars is a popular way of limiting rotation of the rear axle housing. Traction bars mount directly to each side of the axle housing and extend forward like long arms or levers. When the housing begins to rotate during initial launch,the traction bars stop this action, holding the housing in place and converting some of the applied torque to a force which pushes the rear tires into the track surface. By stabilizing the axle housing, wheel hop is virtually eliminated, acceleration is smoother and parts breakage is minimized.
HOW “WHEEL HOP” OCCURS
REAR AXLE HOUSING ROTATION WITHOUT TRACTIONCONTROL
When horsepower is suddenly delivered to the differential, whether from a clutch or a torque converter, the pinion attempts to “climb” the ring gear. This sudden shock of torque causes the entire rear axle housing to rotate backwards in a counter-clockwise direction. This causes the springs to distort, resulting in severe driveshaft/U-joint misalignment.
SPRING REACTION UNLOADSSUSPENSION, CAUSING “WHEEL-HOP”
The axle housing is allowed to continue its rotation until it meets resistance from the suspension/springs, which then try to “snap” the housing back to its original position. As power continues to the differential, the housing is once again allowed to rotate back against the springs. This action/reaction of the suspension, commonly known as “wheel hop,” continues much likea tug-of-war. Instead of launching your car forward, you sit there bouncing around and spinning your wheels.
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UNDERSTANDING SUSPENSION BASICS PRODUCT HEADER
COMPETITION ENGINEERING TRACTION BAR LIMITS AXLE ROTATION
The bolt-on “Slapper Bar” is one of the most basic traction devices available. Originally pioneered by Bill “Grumpy” Jenkins in...