Recording turn segment times allows direct comparison of your times to those of your competitors. Turn segment evaluation does a better job of telling us when we are correctly set up than the evaluation of lap times that include straightaway acceleration.
How to Measure Track Performance
Once we hit the track, we need to be able to measure our on-track performance. There are two components of speed: the motor/drivetrain combination that gets us down the straightaways, and the chassis setup combination that gets us through the turns. Since we work on these separately, we need to measure them separately.
A car can be the fastest one in the turns but not up to par down the straights for a number of reasons. If we have lap times that include turn segment times, we can compare our times to that of our competition. Turn segment times tell us all we need to know about chassis setup experimentation.
We should always take turn segment times in addition to total lap times and compare both with other fast cars. Remember, if we can improve the midturn speeds, we can also improve the straightaway speeds. It is generally accepted that speed gained in the turns is carried all the way around the racetrack.
If we use previously run tires, the age of the tires must be taken into consideration when making comparisons to other cars. If we start on stickers and then run 50 laps of testing, we can expect to lose time to the tires. If our lap times stay consistent, then the changes we are making are probably enhancing our performance. Eventually switching to newer tires will show the positive results of our changes.
It is not a good idea to chase a competitor who has newer tires than ours. If we struggle to make adjustments in an attempt to make up the three- or four-tenths difference, we could put our setup out in left field, never to return.
Some teams use unsupervised tests as a chance to "cheat up" the car to go fast. If an opposing team is too fast, we should not try to keep up by making wholesale changes. Once that team returns to regular competition, where the rules must be observed, the times will return to normal.
Testing also includes driver orientation to a new and different racetrack. Here, we see a strange configuration for a track that has a smaller radius in Turns 1 and 4 and a larger radius in Turns 2 and 3. This arrangement will take some getting used to, as the driver must learn to accelerate sooner in 1 and 2 and brake less and later going into 3 and 4.
The First Set of Runs
The driver should initially make several slow five-lap circuits and then five faster circuit runs to shake down the car. This establishes that the brakes work as expected, the wheels are on tight, the air will stay in the tires, and there are no water or oil leaks. The transmission and rearend lubricants will also be brought up to temperature. Two more five-lap runs must be made following the initial outing in order to get meaningful tire temperatures.
After each of these runs, we record the tire pressures and/or temperatures, tire sizes, engine water and oil temperatures, and the number of laps run in each session. Then, we make hard copy records of the data in addition to digital records (stored in the tire temperature/pressure box or on a computer). It is fine to have digital records, but we all know how easy it is to lose digital information. Doing both is the best way.
Once the driver is confident that the car is sound, longer and faster runs can be done. In the next series of runs, the driver needs to stay out at least 10 laps so that the tire temperatures will be sufficient to show how the tires are working. Unless the car has a serious handling problem, this should not be an issue. The car should be viewed from a high vantage point. We should pay attention to how the car looks, where the driver's hands are positioned, and how far the wheels are turned while in the middle of the turns.
The crew must communicate the changes and the reasons for those changes to the driver. That way he or she can know what to expect the next time out on the racetrack. Feedback from the driver to the crew is essential in order to properly evaluate the setup.
Evaluation Time
The next step involves evaluating the tire temperatures, pressures, and overall handling balance. Quick adjustments are made to the front tire cambers and all four tire pressures if the temperatures dictate doing so. The handling cannot be properly evaluated if these issues are not resolved right away. No chassis adjustments will be made until we have taken care of the tire issues.
Excess steering input at midturn, inability to keep the car low in the turns, and a car that snaps loose off the turns are all indications of a tight setup. The driver should run the turns at a speed lower than normal and note the position of his or her hands. Once the car is up to speed, the driver should again note hand position. If the steering is significantly different, the car is either tight or loose.
We should record driver and crew comments regarding handling and engine performance. If the car is not neutral, we will make changes to improve the handling while working to maintain a balanced setup.
There is a difference between handling balance and dynamic balance. The car is neutral when it is neither tight nor loose. We can easily adjust most cars to make them neutral. This may make the car faster, but it is not our primary goal. The car needs to be neutral in handling, and the front and rear suspension must be in sync. When both ends of the car are working together, we will truly have a balanced car that is fast and consistent.
Significant tire information is written on the sidewall of the tire so that it is easily apparent. This tire is from the right front and is from set three. It has been used at Lonesome Pine Raceway and was first run on June 29.
Mid Turn Performance First
We must always evaluate and correct the midturn performance first. Balancing the car at this steady state point on the track will also help balance it on entry and exit. Steady state is defined as a condition in which the car is neither accelerating nor decelerating. So the dynamic effects of longitudinal weight transfer from braking or motoring off the corner are not affecting our evaluation at this point in the test.
We can interpret the balance of the car by evaluating the tire temperatures. The easiest way to make a car neutral is to adjust the crossweight. Crossweight is the percentage of the total weight of the car that is supported by the right-front (RR) and left-rear (LR) tires as read on the scales. Lowering the RF and LR corners while raising the LF and RR corners reduces crossweight and loosens the car. All four corners must be adjusted to cause a change in crossweight.
After we have made the car neutral in handling, we need to make a couple of hard runs and note the tire temperatures. The dynamics of the front and rear suspensions working with or against each other will show in the tire temperatures. The LF tire will be near the same temperature and working as hard as the LR tire in a balanced setup.
If the LF tire is the coolest tire on the car (by far the most common condition), then changes should be made to the setup to help heat that tire up by making it work harder. With the popular big bar and soft spring (BBSS) setups, the opposite is usually true. The LR tire might be the coolest tire on the car, and we need to make changes to cause the left-side tires to be the same.
Tire wear can tell us a similar story when racing on dirt. Dirt teams rarely take tire temperatures. They feel the tires for temperature, so it must be somewhat important. But tire wear can also tell us how hard a tire is working.