Many top teams have sorted out their setups in just the way we will outline here, and they
Throughout your career, whether you're a driver, a car chief, or a crewchief, sooner or later you will have to deal with an unfamiliar race car. When faced with setting up or driving a race car with which you have no previous experience, often at the spur of the moment, there are certain rules and steps to follow in order to quickly get a handle on the car and set it up to be a winner.
As I watch others dial in a new or different car, and having worked with "new to me" race cars myself over the years, there has evolved a method and defined routine for becoming knowledgeable about any chassis and then fine-tuning it to what it should be.
I have included the driver here because he often steps into difficult situations in which he is expected to make the car perform better than the last driver. Having knowledge of these methods will help him get the car straight and up to speed quicker and make his job easier and more successful.
The following are the steps, in order of importance (with most critical first), for evaluating and redesigning an unfamiliar car.
Last season, Bobby Gill had to climb into a new car. The process may have been similar to
The absolute first thing we need to know about an unfamiliar car is the condition of the various mechanical components. We do not need to be tuning the setup and handling on a car that has bound control arms, broken shocks, worn or broken steering, a bent chassis, and cracked welds.
I have spent lots of time and owner's money on a car that the crew said was in top mechanical condition only to find out that the right-front shock was basically frozen and the steering box was very tight. We spent valuable time trying to fix the "handling" problem when in fact it was component failure that caused the car to not perform the way it should have.
Ask very pointed questions to gain knowledge of the car. "Do you know where the moment center is located?", "Have you had your shocks tested lately?", "Do you have any Ackermann in the steering system?", and "How often do you change the brake fluid?" are examples of queries that get right to the point. The answers will tell you just how much the crew knows about the car and alert you to possible trouble areas up front.
Go over the car thoroughly and inspect and cycle the brakes, shocks, control arms, steering, ball joints, and all other moving parts. Ask when the rearend was last serviced. Once you are convinced that all is right mechanically, you can move on to the next step.
Top car builders have come to understand and accept the importance of the front moment cen
The very first thing we work with is the front geometry. There are two areas of geometry that are most important. Those are the moment center locations (static and dynamic) and the camber change characteristics.
In today's racing environment, most of the top dirt and asphalt race teams, as well as some of the top car builders, are very much on top of the moment center (MC) design in their cars. Long gone are the days we even hint at thinking that MC location is not important. It is extremely important, and the small amount of time spent on finding the location of our MC and making changes to improve it are all well worth the effort.
If you are working with a car and you don't know where the MC is, then the chances are very good that the car will never reach its true potential if the MC location is off. It all starts there. You must take the time to evaluate this area of the car. No amount of other chassis adjustment will overcome MC problems.
Regular maintenance on such items as the quick-change rearend helps keep the mechanical br
The next geometry consideration is camber change. Camber change is a combined product of the motion of dive and rol of the front end through the middle one-third of the turns. If we know that, or can adequately make an educated guess at the motion by observing the car, then we can enter dive and roll numbers into a computer program and see the true camber change.
Camber change is dependent on chassis dive and roll combined, so knowing those movements will lead us to the correct picture of what is going on with camber change. Camber change curves that use the bump of the wheel only represent half the picture.
I recently visited the Northeast and observed a team running both an SK Modified as well as a NASCAR Whelen Modified Tour car. This is a top team, and I was asked by the driver to observe one of the SK cars in practice at Stafford Speedway. The right-front tire, on entry and through the middle of the turn, was transitioning from a negative 2.5 degrees to some amount of positive camber.
The crewchief had carefully gone over the camber change numbers in a geometry program but used the wrong dive and roll figures. When he re-entered the correct numbers, the camber loss was very evident. With relatively small changes to the upper control arm angles, the car became much more competitive. If this can happen to a top team, it can happen to you and me.
The pickup points in the front of the car move in relation to chassis motion. That motion
Once the front end geometry is taken care of, the next step is to align the tires. Included in the overall scheme of alignment are: toe of the front and rear wheels, rearend alignment and location (laterally), Ackermann steering alignment, and rear steer characteristics.
Any one of these four alignment issues can and will, if not properly adjusted, have a detrimental effect on your handling that cannot be fixed with any amount of spring change, weight distribution change, or Panhard bar movement.
Toe checking is quick and easy. Start there and remember to check the rear end for unwanted toe, too. Then, move on to stringing the car to see if the rear end is square to the centerline and that the right-side tire contact patches are inline. Trailing or leading the right-rear wheel is a crutch for a setup that is not balanced.
It appears that this car has camber change problems with the right-front (RF) tire. The le
Ackermann used to be a tool to help an unbalanced car turn when the left-front tire was not being loaded to its full potential. As we have evolved over the past 10 years into learning how to balance the setup where the left-front (LF) tire is now carrying more load and working harder, we can now eliminate the Ackermann effect. If we do not, the car will push as the front tires fight each other and try to go separate directions.
Rear steer is another alignment issue because it can alter the alignment of the rear end as the chassis dives and rolls. There are times when we want and need some amount of rear steer in our cars. We need small amounts when racing on asphalt and larger amounts under some conditions when racing on dirt.
We need to be very careful with the rear steer adjustments and make sure we know what is happening with our rear steer and the amounts involved. The current trend on both asphalt and dirt is to minimize the amount of rear steer. Top dirt Late Model cars are getting away from allowing the left-rear (LR) tire to fold up under the suspension links to create an excessive amount of rear steer. By working with the MC design and developing a more balanced setup, they can stop using this crutch to help the car turn.
One of the easiest and most accurate methods to check for the presence of Ackermann steeri
Once we have checked out and optimized the mechanical efficiency of the car, evaluated and re-designed the front end geometry, and aligned the car properly, the next step is to decide on the spring rates for the car. Here are some guidelines.
We need to decide on the overall stiffness we will need in our spring package first. Are we running a conventional setup or soft springs with a large sway bar? What are the track conditions as far as traction availability and banking angle? Are the transitions extreme?
The very first consideration is spring stiffness. Then we can go on to determining spring split at both ends related to track banking angle and the need for bite off the corners. A flatter track with less grip will require softer springs so the car is more compliant in order to maintain traction during the transitions of entry and exit. There will be less g-force, and a stiffly sprung car may slide rather than maintain grip.
A high-banked track is more forgiving for the transitions, and we may need a stiffer spring package because the g-force is higher, and that produces more downforce and chassis travel. We must keep the frame from bottoming out on the racing surface. Once we decide on the overall spring stiffness, we determine the front spring split.
Square your rear end and line up those right-side tire contact patches. Basic alignment is
On flatter tracks, and this goes for both asphalt and dirt setups, we might want to run a stiffer left-front spring. This helps with the transition into the corner on entry braking. If we brake straight ahead with a softer right-front spring, the car will roll to the right as the RF spring compresses more than the LF spring, motion ratios being the same. This matches the eventual roll direction of the car as it approaches mid-turn and feels good to the driver.
For medium to high-banked tracks, it is best to run even spring rates across the front and, as the banking increases, begin to stiffen the RF spring over the LF spring. This decreases the desired roll angle of the front end and increases stability. A Cup car racing at Daytona can achieve roll angles of under 1 degree through the use of spring split without using a large-diameter sway bar.
The rear spring split is dependent on three factors: 1) track banking angle, 2) amount of traction needed for acceleration, and 3) overall spring stiffness (i.e., conventional asphalt setup, or the Big Bar and Soft Spring setups).
Ultra-high banked tracks such as the 26-degree Bristol (TN) Motor Speedway require spring
A typical Late Model setup for low-banked tracks might look something like this. This migh
The high-banked setups require heavier spring rates as well as stiffer right-side rates th
Photo by Keith Cyr
The track banking angle has an influence on traction and roll angle. There is a high amount of downforce associated with high banking and as such, a spring split in the rear of the car introduces additional roll angle influences. A split where the left-rear spring is less than the right-rear spring causes the rear to roll less. A softer RR spring will cause the rear to want to roll more.
The high banking and associated higher downforce puts more load on the rear tires to the extent that there is seldom a traction problem when exiting the corner. So stiffening the RR spring is acceptable for high banking angles, whereas the stiffer RR spring may hurt turn exit performance with a lower-banked track.
With low banking angles, we usually have a need for better bite off the corners. Using a softer RR spring helps because, as the car transfers load to the rear under acceleration, the stiffer LR spring causes a momentary increase in the crossweight percentage while the car is accelerating. This tightens the car so that more throttle can be used on exit.
The rear springs greatly influence the rear's tendency to roll. Stiffness is secondary to the spring split in roll influence. So, to keep the car balanced, the Panhard bar must be raised in conjunction with softening the RR spring and/or stiffening the LR spring. In a split where the LR spring is less than the RR spring, the Panhard bar must be lowered to maintain the same roll tendency.
Most shock manufacturers and many independent dealers offer shock maintenance and shock re
When we have sorted out the geometry issues, aligned the tires, and chosen the spring rates, we then, and only then, work with the shocks to fine-tune the transitional handling.
Most top shock company reps will tell you right up front that you need to sort out the basic setup before working with the shocks. That means getting the car to handle through mid-turn first. Then you should work on turn entry and turn exit with the shock package.
Make sure those shocks are working properly. A simple test is to push down on each shock to feel the smoothness of the motion. The resistance will only be valid for low-speed jetting, but we are trying to determine if the shock will cycle without sticking. Having the shocks dyno'd by a professional shock technician is a better idea. That way you will know the exact rate for each increment of speed of shock movement.
Shocks control the speed at which each corner of the car will move when the dynamics of turn entry and turn exit come into play. Shocks do not influence weight distribution at steady-state, mid-turn attitude, but they do regulate the distribution of loads during the transitional periods.
If we slow the motion on one corner of the car as load is transferring onto that corner, momentary loading will increase on that tire as well as the diagonal tire. On turn entry under deceleration, the RF and LR tires will gain load if we stiffen the compression of the RF shock. This will tighten the car on entry while load is being transferred to the front.
If compression is increased at the LR, then as the load is transferred to the rear while under acceleration, the LR and RF tires will gain excess momentary load while the load is transferring.
The rebound side of the shock can cause reduced loading of a corner of the car when load is being transferred off of that corner and the rebound resistance is increased. This reduces the loading on that tire as well as the diagonal tire. Tune accordingly.
The radius of the turns and the track banking angle determine the amount of rear tire stag
There are several settings that should not be used as tuning tools. They are as follows: rear stagger, tire pressure, camber, rear alignment, Panhard bar split (except on dirt under some slick track conditions), and excess brake bias settings.
The rear stagger should match the average track turn radii. The tire pressures should be set to even out the tire temperatures across the tire surface. The tire cambers should be set to also even up the tire temperatures with a preference to slightly higher inside (toward the inside of the racetrack) temperatures. The rear alignment should always be square with the chassis. Panhard bar split should not be used to tune the car. There are jacking tendencies with bar angle that move load around in the turns, and this makes the car inconsistent. Never try to fix a tight-in problem with excess rear braking bias. Fix what is causing the car to be tight in, such as setup balance, shock rates, or Ackermann.
Look to past articles we have presented in Circle Track for more detailed explanations for each area of chassis setup. If you can quickly evaluate that "new to you" car in the order given here and then make the right corrections where necessary, your chances for success will be greatly increased, and the level of frustration that often accompanies working with unfamiliar cars will diminish.