Stock Car Practice Sessions - Track Testing Tips

A stock car test, or practice session, is the place to discover how the car is working and make changes that will hopefully improve performance. The process may not always go in that direction, though, and must involve a routine that will bring mixed results and might actually cause the car to slow down.

A real life example is a private test that was done at a Midwest track in preparation for a final race in a NASCAR Late Model series that would determine the championship for a team. The consultant hired by the team had done all of the correct preparation, and the car was fast right out of the truck. By 11 a.m., the car was both fast and stable by virtue of the lap times, tire temperatures and wear, and the comfort level of the driver.

By all accounts, there was nowhere to go but backward. So the consultant used the time to try all sorts of combinations of spring rates, spring splits, shock rates, sway bar sizes, etc. for the next three and a half hours. The car did nothing but go slower while the handling went from bad to worse.

It was now approaching 4 p.m. and time for a qualifying run on stickers. The owner and crew were understandably nervous. The consultant instructed them to put the car back where it was at 11 a.m. and mount the stickers. The car went out, handled fine, and was very fast.

The driver later questioned the process and inferred that they had wasted over three hours of testing. He was told that once the ultimate setup was achieved, all further testing would have a 99 percent chance of making the car worse, but the process just might find small gains as well. We would never know unless we tried.

All testing and practice involves trying different combinations of setup and chassis geometry that might make the car faster. We can be searching for an unknown by making intelligent choices in reasonable directions. What you don't want to do is start out with a car that's not well known and throw springs and so on at it, hoping for a miracle. The top consultants will never work with a car about which they don't have critical information.

It is most important to know your car before you go to the track for practice or testing. This means the front and rear geometry have been evaluated, the car is aligned, and a dynamic analysis of the spring combinations to balance the two suspension systems has been done. We should have tested and dyno'd the shocks, rated the springs, checked the steering system for Ackermann, weighed the car, and prepped the motor.

If you have not been there before, you must consider the type of racetrack. If it is of a different banking angle than you are used to, a different moment center design might be in order. High-banked tracks have little need for traction-enhancing technology, so plan out your rear steer characteristics and ride height if excess chassis travel is an issue. If the track is flatter, include methods of creating bite off the corners into your planning.

If the length of the test track is different from what you're used to, calculate a rear gear that would be in an acceptable range, or contact a team that has run the track and ask about gear ratio. If you are testing on dirt, pick the correct tires for the anticipated conditions.

In the days before leaving the shop, prepare a plan of attack to define which changes will be made in which areas. The plan should be discussed with the entire crew so they can give input on the process and know the direction in which the test will go, thus be prepared in their particular areas of expertise.