Example Six--asphalt touring Late Model on a flat track
This car has a front MC that is too far to the right of centerline for a flat asphalt track, stiff front springs, and the rear spring split is too much. The roll angles are 1.8 degrees different and that makes for a very unbalanced and inconsistent setup. This car might be fast for a few laps, but in the long run, the lap times will fall off quite a bit.
These changes will balance the car while still providing sufficient bite off those flat corners. A high crossweight percent range works best to help with exit performance.
1. Change the front spring rates to: LF = 350, RF = 325.
2. Change the LR spring to: LR = 185 (the split is reduced to 10 pounds versus the original 25 pounds).
3. Raise the Panhard bar to: 9.50/10.75.
4. Move the dynamic MC width to the left to end up at 4.0 inches right of centerline.
5. Use a high crossweight range (more equal to the left side weight percentage).
The reverse spring split on the front helps the car on entry to the corners. If we were to run a stiffer RF spring than the LF, the car would begin to roll to the left on braking into the corners because of the softer LF spring. As the car continues to drive farther into the turns, the front must reverse and roll to the right. This gives the driver a very uncomfortable feeling that can best be described as a "flip-flop" sensation.
When we change to running a stiffer LF spring, as we brake into the corner the car will begin to roll the same direction we normally would see at mid-turn. The transition is smooth and the driver will have more confidence on entry.
The rear spring split with the softer RR spring helps promote traction in the rear by loading the crossweight percent as weight is transferred to the rear upon acceleration. Usually a 10- or 15-pound split is sufficient to provide the desired effect where a split of 25 or more pounds is often too much.
The Panhard/J-bar can remain relatively low because of the wider rear spring base that is a characteristic of these cars. On a solid-axle rear suspension like we use in stock cars, the wider the spring base (farther apart the rear springs), the more resistance to roll the car will have at the rear suspension. To balance this type of car versus a stock type of Late Model, we need to run a lower rear MC (which produces a longer rear moment arm) to compensate for the wider spring base.
The front MC change (moving the MC to the left) makes the front suspension "feel" softer and more efficient and want to roll to a greater roll angle to exactly match the rear suspension desired roll angle.
Example Seven--asphalt touring Late Model on a high-banked track
Many teams who run the flatter tracks mostly will try to set up their cars the same way when at the higher-banked racetracks. The higher banking produces much more downforce, and the arrangement of springs that works best on the flatter tracks won't work well on the high banking. The higher the banking, the worse it gets. Rear spring split with the LR stiffer than the RR cannot be used because the higher g-forces cause more downforce and magnify the effects of the spring split. This makes the cars very unbalanced.
At the high-banked racetracks, we experience more chassis dive and less chassis roll. Excess camber change is a result, but less detrimental to traction because of the high amount of downforce and increased traction caused by more force being exerted on each of the four tires. Here are the changes we would make to the setup to balance the car for a 14-degree track:
1. Reduce the front spring split to: LF = 375, RF = 400.
2. Even up the rear springs: LR = 200, RR = 200.
3. Raise the RR Panhard bar to 11.50 (which raises the rear MC and increases the split in the two ends of the bar to compensate for the increased travel on the RR corner due to the added downforce.
4. Change static cambers on the front--increase the LF positive camber and decrease the RF negative camber.
5. Use a low crossweight range (from about 50 to 52 percent).
Example Eight--Asphalt Touring Late Model on a very high-banked track
The following is where we would want to be if the track banking angle was much higher, at say 26 degrees. The car will have a lot of traction due to the high amounts of downforce and therefore the cornering speeds will be high. The resultant force (a combination of gravity and the lateral cornering force called centrifugal force) will be in a direction that lies between the front tires. This results in a lot of vertical chassis travel and little chassis roll. Traction is never a problem unless the setup is very unbalanced. A balanced setup for a very highly banked race track for an asphalt Late Model.
Note that the front spring rates are much higher and the rear spring rates are both higher and split to a greater extent. Both of these could be even higher if the radius of the turns is smaller. The front MC is farther to the right, the average Panhard bar height (rear MC height) is higher, and the g-forces are up considerably to 2.2 g's. The front suspension travel will average in excess of 3 inches and the rear suspension will travel upwards of 5 inches or more. If your car normally has a 4-inch ride height, then the car must be raised or it will make contact with the track surface.
The starting cambers might be: LF = +3.5, RF = (-) 1.0. That is because of the high amount of chassis dive the car will experience that will reduce the positive LF camber (become less positive) by 3 or more degrees and increase the (add to the negative amount) RF camber by about the same amount.
Again, let me say the changes we have made to these sample cars are the same as we have made to real cars in actual competition. It doesn't mean you need to run out to your shop and put these setups in your car. Remember the directions we have taken and trends we have described related to the different types of race cars. The hot tire temperatures, as well as the tire wear, will be an indication of how close you come to a balanced setup.
The differences between these cars and yours that might cause these setups not to work for you include: a) center of gravity height; b) front moment center (roll center) location; c) front end motion ratios for spring mounting; d) weight distribution; and e) front and rear spring location and spring angles.
All race teams need to know certain basic information about their cars. Learn the tendencies that make a car's suspension want to roll more or less and try to match the ends for a more balanced setup. Know your front geometry settings, especially the moment center location and camber change characteristics. If you do, finding that sweet spot related to a winning chassis setup will be a much easier process. Above all, be willing to take control of your chassis, and do not be afraid to make changes to improve the geometry, the alignment, and the balance of your setup.