With the rearend steering to the left of centerline, the rear of the car will want to run
8. Rear Geometry Challenges
Rear steer in a circle track race car is a condition caused by suspension movement. Under the right conditions, RS can be beneficial and enhance performance. Under the wrong conditions, it can ruin your handling. We need to have a solid understanding of what produces RS and what effect RS has on the handling in our cars.
The first and foremost thing to understand about RS is that it is caused by rear suspension movement. As the rear corners of the car move, along with the controlling arms that locate the rearend fore and aft, each side can move the wheel on that side forward or to the rear.
Obviously, if both of the wheels did not move or moved in the same direction by the same amount, we would have zero rear steer. It is when one wheel moves more than the other that we have rear steer.
On asphalt, don’t make large changes to components that influence rear steer. Make small adjustments if you feel you need to and once you find the correct amount of rear steer, stay there and tune the handling with the other components.
When racing on dirt, watch the conditions and be prepared to make changes accordingly, not just to the setup, but also related to rear steer. That way, the car will stay fast and balanced throughout all of the changing conditions.
9. Bite Challenges
If there is one thing we usually can’t get enough of it is forward bite in our race cars. We need to learn ways to make the tires stick while we are under power off the turns.
An opposing pair of tires (tires on the same axle at the same end of the car) will develop maximum traction when they are equally loaded. The closer we can get a pair to being equal, the more traction they will have.
The shape of the track for both dirt and asphalt can influence the available traction in several different ways. As we apply power, we need to know a little about how the track is banked, how the banking angle is changing coming off the corners and how the radius of the turn might be changing.
The tracks we worry about getting off the corners are the ones that are flatter and with less surface grip. When all available and useable methods of promoting traction have been applied, the car may still be difficult to apply power to without losing rear traction. In that case the drivers must use their skills to help prevent loss of rear traction coming off the corners.
Many top drivers have perfected the art of throttle control to help maintain traction. This means that if the driver knows he/she can’t apply full throttle without the rear tires spinning, then they will work to apply just enough power to accelerate without breaking the tires loose.
When we are cornering, a lateral acceleration force commonly called a G-force tries to ove
10. Weight Distribution Challenges
In order to really understand race car handling, we must know something about the load distribution on the four tires and how those loads change through the course of a typical lap. When we fully understand the principles of weight distribution and load transfer, we can better plan out our setup so that our car will have a better load distribution when cornering.
The extensive studies of the properties of tires all came to the conclusion that a pair of tires will produce more combined traction when they are evenly supporting the weight upon an “axle.” The axle term is used here to mean any two opposing tires in a suspension system.
The relationship between the two suspension systems will dictate how that transferred load ends up being distributed upon the four tires.
As we make positive changes to bring our car to a more balanced setup, we will need to make corresponding changes to the crossweight percent. Reducing front roll stiffness causes more front traction and the crossweight percent must be increased to keep the car from becoming loose. Increasing the rear roll stiffness will also cause the same effect, so too is the need to up the crossweight percent.
Don’t get stuck on a particular crossweight percent number. Be flexible and understand what is happening when you make those spring rate changes or Panhard bar movements or when you move weight around in the car. If you understand the influence of weight distribution and load transfer, you can then make more intelligent chassis setup decisions.