This pull bar has a long spring...
This pull bar has a long spring that probably will not coil bind as the car accelerates. This serves to improve the bite throughout the entire acceleration zone. These units must have a shock attached to slow down the movement on acceleration and especially braking.
As the brakes are applied, the caliper grabs the rotor and the motion of the wheel/rotor tries to rotate the spindle. This force is resisted by the ball joints. The upper BJ is being forced in a forward direction, and the lower BJ is being forced in a rearward direction.
If we arrange our arm-shaft angle, from a side view, correctly, then as the car dives the upper BJ would need to move to the rear, and the bottom BJ would need to move to the front. Since the anti-dive forces are in the opposite directions, there is a serious resistant force to dive that helps prevent the front suspension from moving quickly.
The amount of resistance is directly related to the degree of side-view shaft angle we put in our control arms. The left-side suspension should be designed with about half the angle of the right side in a conventional design. This has an overall benefit on dirt by reducing the sudden camber change that can cause the front end to lose grip and push.
The upper control-arm attachment...
The upper control-arm attachment on a dirt late model offers the opportunity to easily remount the arm for anti-dive and redesigning of the moment center. All you have to do is weld on a new set of bungs in the desired location and reattach the control arm. We've done just that with many late-model cars.
Anti-squat results from the pull bar trying to straighten out or become more horizontal as the car accelerates and the rear end desires to rotate. The more pull-bar angle you have, the more anti-squat there is. The lift arm also creates anti-squat and can actually lift the rear of the car on acceleration. Lateral movement of the front end and/or rear of the lift arm can alter the loads among the two rear tires upon acceleration.
10. Aero Package Some years ago, racers discovered the need for better aero designs. Just look at the dirt late-model cars and how they have evolved. The front ends are wedges that scoop the oncoming air up and over the car. The wheelwells are shaped to route air out and away from the front tires, creating downforce.
The degree to which you need to get involved with aero for your car depends a lot on what you run and where. Aero influence varies with the speed of the vehicle. There is an algebraic increase in both drag and downforce associated with increases in speed through air. That's why a car with twice the horsepower does not go twice as fast.
Try to understand how aero downforce is created, then configure your car so that you take advantage of every area where you could produce more downforce. On dirt, we need the most loading we can get on our front tires, and aero generated load is not weight we have to accelerate.
Dirt cars have been modified...
Dirt cars have been modified over the years to a more aerodynamic wedge shape where the oncoming air is directed over the top and around the sides of the hood, not under the car. This produces a significant amount of downforce due to creation of low pressure areas under the hood. Note the flare around the wheelwells.
Conclusion As every dirt racer knows, dirt is a tough medium to set up for. Have your car set up correctly for the basics of alignment and geometry. Develop a proper approach for the tracks where you intend to race. Be prepared and willing to make changes to your setup when track conditions change. With all forms of motor racing, remember that success comes in stages.
Improving your finishes is where you start on the road to winning. Don't think that just the work done to improve the setup will quickly lead you to Victory Lane. Learning how to win is a process; when the moment is right, you'll find yourself waving that checkered flag on the Victory Lap.