This pavement car is well...
This pavement car is well balanced and able to drive right on the white line at the bottom of the racetrack. The consistency that a balanced setup provides will create the opportunity for winning. This team won this race.
Chassis setup, especially the tuning part at the racetrack, is largely a matter of experience. Over the years, the most sought after crew chiefs in stock car racing were the ones who have demonstrated the ability to make quick and accurate decisions needed to solve handling problems.
Today, as a direct result of a lot of research and development taking place over the last few years, we might look at these common fixes in a little different light. Basic chassis setup techniques are common to both dirt and asphalt racing.
The difference in the track surfaces creates special problems for each, but the raw basics remain the same. The following is a list of "dos and don'ts" related to creating a good, balanced setup and solving basic handling problems. We will note where differences may occur related to dirt or asphalt.
Unstable Entry-Many times a driver will feel very uncomfortable with entering a turn. The car just does not take a good set as we begin to brake and turn left. This feeling causes him/her to back off early and not go as deep into the corner as other cars.
At higher banked tracks, say 12 degrees or more, a setup utilizing a stiffer right front (RF) spring will tend to load the crossweight percent on entry as the car is braking and starting to turn left. That is because the LF will dive more than the RF, which will load the RF and LR tires momentarily. This feels good to the driver and gives him confidence knowing the rear end will stay under the car.
A stiffer compression setting on the RF shock can produce a similar weight and aid deeper entry into the corner by momentarily loading the cross, just like the stiffer RF spring does.
At flatter racetracks, especially on dirt, we have a very different cause and solution to the problem. When we brake going in the corner on a flat surface, we want the car to begin to roll in the same direction as it ultimately will in the middle of the turn. If we set up the car with a stiffer RF spring, the car will sort of flip-flop, first starting to roll left when braking and then right as we roll through mid-turn. This is sometimes visible to the observer watching from outside the car.
The solution is to run a stiffer LF spring. As we brake into the corner, the RF spring will compress more than the LF spring and the car will begin to roll to the right. As the car enters the mid-turn, it will continue to roll more to the right and the transition will be much smoother, enabling deeper corner entry.
Loose Entry-A car that is loose on entry to the corner can have several problems. If the car is severely loose and nothing seems to help, it is almost always rear end alignment that is the problem. Typically, the rear end is pointed to the right of the centerline of the car and wants to swing right as the car is steered left, much the same as a hook-and-ladder fire truck does when the guy in the back steers right going around a corner. The car will feel much the same as this. Regardless of how straight you think the rear end is, start moving the RR forward 11/48 inch at a time until the car is no longer loose-in.
At racetracks with a tight entry, and/or requiring heavy braking on entry, the loose condition is most likely brake bias or shock related. First, try moving the brake bias to the front. If that does not help, then decrease the rebound in the LR shock and/or increase the compression in the RF shock. A common fix to a tight car on entry used to be increasing the LR shock rebound to pull weight off the LR corner. That made both ends loose and corner speeds suffered.
Push on Entry-A car that develops a push on entry may have too much brake bias toward the front end. Another cause that would develop at the same point of heavy braking, and is hard to distinguish from bias problems, is when the shock/spring combination is too soft.
The crew chief can tell a...
The crew chief can tell a lot about the car's handling balance by observation. From this vantage point, he can observe how the car looks as it enters and negotiates the turns.
Notice that this upper control...
Notice that this upper control arm mount has anti-dive built in. Seen just above the upper control arm are the two mounting bolts. The front bolt (to the right in the picture) is higher than the rear bolt.
Special slotted upper control...
Special slotted upper control arm brackets are fitted with offset slugs that allow you to lower or raise the mounts. This car lowered the rear mount by 11/44 inch and raised the front mount by 11/44 inch to make a 5-degree angle in the control arm shaft for anti-dive.