Competition Engineering : Tech Articles

HOW "WHEEL HOP" OCCURS
Rear Axle Housing Rotation Without Traction Control:

fig. 1 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 Unloads Suspension, Causing "Wheel-Hop":

fig. 2 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 like a tug-of-war. Instead of launching your car forward, you sit there bouncing around and spinning your wheels.

Competition Engineering Traction Bar Limits Axle Rotation:

fig. 3 The bolt-on "Slapper Bar" is one of the most basic traction devices available. Originally pioneered by Bill "Grumpy" Jenkins in the mid-sixties, it gets its name from the way it works. One end of the Slapper Bar replaces the stock spring pad and is clamped to the rear axle housing. The front end of the bar is suspended just below the spring eye. When the housing begins to rotate during launch, the bar also rotates until it contacts or "slaps" the spring. (Unlike other brands, Competition Engineering Traction Bars make contact directly below the front spring eye, preventing spring damage). When contact occurs, the Slapper Bar becomes a lever trying to push the axle housing down and planting the tires in the process.

Slide-a-link™:

fig. 3 A revolutionary, patented, completely bolt-on traction device, the Slide-A-Link™, designed for both street and strip use is track tested and competition proven to outperform conventional “Slapper” bars. A solid mounted front plate is installed inside the original front spring pocket and clamps to the leaf spring to provide a positive displacement for the torque that is transmitted from the rear axle through the telescoping bar and special durometer shock pad. These forces, along with improved instant center geometry, provide better weight transfer for increased traction. Free travel and pre-load adjustments are made on the vehicle by adjusting the jack screw at the rear of the bar.

How Ladder Bars Work:

fig. 4 The Ladder Bar is a more sophisticated traction device because it serves as an extremely rigid, bridge-type truss that locates the rear axle housing directly to the chassis. With the axle housing held firmly in place, the torque applied to the differential is now transferred immediately through the Ladder Bars and into the chassis. By using the Ladder Bar to carry power to the chassis, the front end reacts by rising. As the front of the car travels upward, rapid weight transfer is created which "plants" the rear tires and propels the car forward.

Housing Floaters Eliminate Suspension Bind:

fig. 5 When using ladder bars with a leaf spring rear suspension, the axle housing cannot be rigidly attached to the springs. If it were, severe binding of the rear suspension would occur because the Ladder Bar and the leaf spring both travel in separate competing arcs. By allowing the housing to rotate and glide on the leaf spring, the Floating Housing Mount eliminates the bind and allows the Ladder Bars to work the way they were designed.

Wheel-E-Bars^TM Help Control Weight Transfer:

fig. 6 Although Ladder Bars and 4-Links provide lift to the front end by transferring weight to the rear, too much lift detracts from the forward motion and reduces overall performance. Installation of Wheel-E-Bars^TM helps to maintain the correct amount of lift and controls weight transfer to maximize traction.

Ladder Bars vs. 4-Links:

fig. 7 4-Links offer more adjustment over Ladder Bars and can handle higher torque loads. With two bars per side, one on top and one on the bottom, you basically have an open ended Ladder Bar. You can adjust the suspension for different track conditions by manipulating the mounting positions in the frame and axle housing brackets. This gives you the option of making the intersection point, or point of "instant center," as far forward or rearward to suit your particular needs. The point of instant center is the location where the upper and lower links would intersect if imaginary lines extended from the front of the 4-Link bars. Unlike a Ladder Bar where the point of instant center is always located at the bar’s front mounting point, the instant center on a 4-Link changes quickly as the car is launched.

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