When the rearend is out of...
When the rearend is out of alignment, it's pointed either right or left of the centerline of the car. When it's pointed to the right, as in our case in the first test, the car is going to be loose at all points in the turns and very loose off the corner due to the direction of the thrust of acceleration. This can't be fixed with setup changes and must be addressed early on in the test.
We recorded lap times in the lower 17.0s and 17.1s at the end of the test with tires that had approximately 70-80 laps on them. John still reported that the car was loose off in the final two runs. We also noticed that the car didn't want to accelerate well and would later find out that the carburetor was not adjusted properly with the float levels. With better acceleration, our lap times might have been better. I was looking forward to the race.
The Seven-Post Rig Analysis
Refer to the article in this issue for the complete coverage of the seven-post rig test. For the purpose of this analysis, we will report that the team made significant setup changes to the car for the evaluation process at the sevn-post test and then decided to keep these changes in the car to be run at the Concord race.
I was not consulted about this change and only became aware of it after the race. So, our analysis now is one of looking back and trying to sort out what went on with this new and untested setup.
Changes included the softening of the LF spring to 391 ppi, stiffening the LR spring to 375 ppi and stiffening the RR spring to 525 ppi. They installed a 2-inch diameter sway bar, up from a 1.5 inch diameter. This increased the bar rate from 1,020 pounds to 2,750 pounds, or equivalent to installing 3,000-pound front springs to equal the roll resistance of that sway bar change. Now they were much closer to a full blown BBSS setup. Unfortunately, that defeated the original plan.
Concord Practice and Race
The team arrived for the Friday practice before the Saturday race with an untested setup. In my analysis, the car was setup tight. I would have run a larger RR spring and rear spring split to go along with the larger sway bar, and in a talk with Joe Berardi, he agreed. The other significant change was to reduce the LF shock rebound that we found most successful in helping get the car off the corners.
When the car went to the seven-post...
When the car went to the seven-post rig, various changes were made to improve the data the rig generates. These changes were left in the car for the race at Concord. As an untested setup, a lot of work went into sorting it out and making it work in the Friday and Saturday practice sessions. The crew did a very good job working it all out to end up with a very decent handling balance. I'm unsure as to the effectiveness of the dynamic balance of this setup.
In the first runs where the tires showed heat, the car was again loose off and the team made basic setup changes to try to fix that problem. Subsequently, the car was never quite right and the lap times showed it to be off our previous test by 2-3 tenths, even with the correctly adjusted carburetor, newer tires, and the aide of other cars running and laying down rubber.
The tire temperatures looked decent with matching right-side and left-side temps. This would indicate a fairly balanced setup, but with a tight loose condition the tire temperatures can be misleading. In hindsight, the team should have dealt with the transition problem with the shocks, not with changes to the Panhard bar, spring rates, or weight distribution.
To adjust for the tight off condition, the team lowered the track (Panhard) bar, increased the crossweight, moved the right truck arm back 1/16 inch, and made changes to the right front shock. The car ended up still very tight with a development of loose off, or a tight/loose condition. On Friday late in the day, they put on stickers and ran a 16.84.
During the Saturday, race day, practice, the team continued to adjust the car and improved the speed. The car ran a 16.89 with more than 40 laps on the tires and 16.93 and 16.94 laps with 50-plus-lap tires. One of the last comments was that the car was borderline loose. That was a long way from the very tight condition they started with.
An analysis of the final tire temperatures showed that the LF and RR were hotter by about 5 degrees than the RF and LR pairs. This can be an indication of a tight setup being made neutral with reduced crossweight percent. Where the LF and LR tire should be equal and the RF and RR tires equal, the diagonal tires were equal. If you pull cross out of the car to compensate for a tight setup, you end up with cooler crossweight diagonal tires being the RF and LR as we see.