Dan displays one of his good...
Dan displays one of his good luck charms (he has several - we won't go into that here) he acquired last year and reportedly has made a difference, if you believe in such things.
Pete had a list he called the "Team Roster/Duties" that stated in bold print, "DO NOT DEVIATE FROM PLAN." Each member of the crew, including myself, had been assigned a job to do. I looked up and down pit lane and no team had any more order and enthusiasm than this young group.
The crew chief Pete selected for the season was Jerry Perryman, a veteran at Madison. I watched him work with the kids at the shop and at the track and I knew from his patience and understanding ways with these rookies that Pete had made a good choice. Jerry was helped in the spotter's box by his brother, Jeremy, and also brought along his friend and veteran mechanic, Joe Koneski.
We had one hour to practice the car and make any adjustment that might be needed. The first time out, we turned about eight laps and came in to check everything out and take tire pressures and tire temps. The LF tire showed about 25 degrees cooler than the LR tire. This indicated a tight setup and we moved the left side of the Panhard bar up a 1/2-inch. Remember that our split was 11/2-inch and this closed the split to 1-inch.
I think I heard somewhere...
I think I heard somewhere that good luck happens when proper preparation meets opportunity.
Dan took the car back out and we ran about ten laps. When we again checked the tire temps, we had gained heat in the LF, but we were still about 15 degrees cooler than the LR. We moved the Panhard bar up another 1/4-inch at both ends and sent him back out for the final session and ran as many laps as we could.
This last change evened up the left side tire temperatures and produced more heat in all of the tires than we had seen before. This gave us a good opportunity to check cambers in the front. Surprisingly, both the LF and RF showed more even temperatures across the tread, so no changes were made to the cambers.
The team had been running...
The team had been running a light 11/8-inch diameter sway bar and it produced a lot of roll when combined with the front spring rates we were running. So, we changed to a 13/8-inch diameter, medium wall thickness bar that rated around 560 pounds per inch of spring rate. The other 11/8-inch bar was only rated at 280 ppi. So, we effectively doubled our roll resistance influence of the bar with this change.
We did initially show a cool outside temperature at the RF, but this was a result of the crewmember taking a temperature too far out on the very edge of the tire and not penetrating the rubber sufficiently. Once this was corrected and the student tutored on correct placement and penetration of the probe, the temps looked good.
The most important data we got was from the driver. After the last series of laps of practice, he said over the radio, "No more changes, I like the car just the way it is." No one had ever remembered him saying that before they told me. I think by going through the car and checking everything that could affect the setup and making it all right produced a racecar that was easy to tune for dynamic balance.
The reason why we needed to make the adjustments we did was because even with the computer tools we have today, there are still numbers that are hard to quantify. Every car has a different center of gravity height that is very hard to measure. Besides, we still haven't had the opportunity to play with different shock settings. There was one more thing I failed to consider.
Once at the track, the car...
Once at the track, the car was gone over once again and prepped for practice. We only had one hour of practice divided into divisions, so we were able to get in about 40 laps total. This told us enough to make two small setup changes that would be all we needed to satisfy the driver and produce good tire temperatures.
The newer Lefthander rear shock mounts at the top are moved to the rear so the shocks are tilted to the rear to increase the length of the spring base. This is something Wayne Lensing, the owner of Lefthander, and I talked about and I completely understand his reasoning. The end result of that is a dynamic reduction in the spring rate the car actually feels compared to the installed spring rate. The spring was angled back about 18 degrees.
To do the calculations to find the dynamic rate, you take the cosine of the angle and square it before multiplying the result times the spring rate. The cosine of 20 degrees is 0.9511 and that squared is 0.9045. Multiplying that number times the 200 pound per inch spring rate gives us a dynamic rate of 180.9 ppi.
So, the 200ppi springs I installed basically felt to the car like a pair of 180s. That is a significant difference that would necessitate raising the Panhard bar in order to compensate. Remember that springs that are installed at an angle to the motion of the chassis have a softer feel to the car, so take that into account when choosing spring rates.