When battling for position,...
When battling for position, there is a philosophy to our approach to driving that can make the difference between making the pass and giving up.
I have had a lot of experience lately with teams who for one reason or another lack that tad of performance needed to move up. It may be in the setup, maintenance, or driving style. The following are 10 tips that will help us finish this season on a winning note.
The approach to racing is a mental process first and a mechanical process after that. We need to decide what our goals are in the beginning, and the information presented here will help formulate those goals. We need to step back and look at the big picture, which includes where we stood with our competition during the first half of the season, our experience level at this point in time (our realistic expectations are directly tied to that), our level of readiness, and finally, having the right tools and equipment to get the job done.
This sketch shows a typical...
This sketch shows a typical situation for a stock car. The rear end is square to the right-side tire contact patches, which are in turn in line.
1. THE 99 PERCENT RULE
If we race long enough, we will eventually stumble upon a setup that wins and may eventually provide us with that coveted championship. But racers are racers, and we all like to experiment. So we lose track of the setup that might have won the first race of the year. One very important aspect of race car setup is the 99 percent rule. When ours is the fastest car on the track and we're winning races, any change we make has a 99 percent chance of slowing the car down.
We must keep good notes and refer to those notes before, during, and after making any changes. We should reference how fast the car is on short runs and on longer runs. Two setups may be equal on shorter runs, but one may be more consistent and that is the one we need to stay with. Most teams are only after the fastest lap setup, but they'll get beat time and time again by cars that are more consistent and faster at the end of the race.
Driveline alignment is an...
Driveline alignment is an important factor in performance and reliability. If you have replaced components on your car and/or made adjustments all year, make sure your pinion/driveshaft/transmission output shaft angles are correct. This affects not only rear-wheel power, but also the longevity of the driveline system.
2. ALIGNMENT ISSUES
Alignment issues can hold a team back for a long time. Most teams work with spring rates, weight distribution, Panhard bar height, and so forth to try to solve setup problems. But if the alignment is off, no changes to the usual setup parameters will overcome misalignment. Here are a few common alignment problems.
Rear and Right-Side Alignment
If the rear end is not aligned properly, the car may be either tight or loose in all three phases of the turns.
One of the very first tasks in setting up a race car is to make sure all of the alignment issues have been corrected. The rear end should be at right angles to the chassis centerline, and the right-side tire contact patches should be in line.
Ackermann, as well as alignment,...
Ackermann, as well as alignment, can be checked using a quality laser system or simply by using a string. For Ackermann, string out about 10 feet from the tire sidewalls with the wheels pointed straight ahead. Make a mark for the left and right wheel. Then turn the wheels about the same as when the car goes around the turns. Make another set of marks. There should be a difference of less than 11/42 inch between the two sets, with the left more than the right.
In the front-end geometry, there is a condition called Ackermann. This is an effect that increases the amount of toe-out in our race cars when we turn the steering wheel.
The opposite of Ackermann is called reverse Ackermann. That is an effect that causes a decrease in the amount of toe-out as we steer and can actually cause the front tires to end up with toe-in if the effect is severe. It is possible to have Ackermann in our steering system when we steer left and reverse Ackermann when we steer to the right.
With excess Ackermann designed into our cars, on purpose or not, we can gain a lot of toe-out, which causes our front tires to work against each other. When this is severe, the front end will push and no adjustment to other setup parameters will seem to help the situation. When running balanced setups that work the left-front tire, we must eliminate most of the Ackermann.
In the common asphalt setups of today where we use a larger sway bar and softer springs (BBSS), the presence of Ackermann effect could be even more detrimental. As we put more and more load on the left-front tire, the negative results of Ackermann become more detrimental.
The sideview angles of the...
The sideview angles of the upper and lower control arms determine the amount of antidive or prodive. The upper arm must be angled with the front higher than the rear, and the lowers must be angled with the rear higher than the front in order to have antidive. With prodive, the arms are positioned with the opposite angles.
3. CAMBER CHANGE
A car that is loose on entry to the corner can have several problems. If the car is severely loose and nothing seems to help, it is almost always rear-end alignment that is causing the problem. If the rear end is pointed to the right of the centerline of the car, it will tend to swing to the right as the car is steered left, much the same as a hook-and-ladder fire truck does when the guy in the back steers right going around a left-hand corner. The car will feel much the same as this.
Regardless of how straight you think the rear end is as this is happening, start moving the RR forward 11/48 inch at a time until the car is no longer loose-in. Most of the time, we don't have the facilities or the time to re-align the car at the racetrack. So we do this quick fix and later re-measure the car at the shop.
At racetracks with a tight entry and/or requiring heavy braking on entry, the loose condition could be brake bias or shock related. If you think the rear brakes are overwhelming the front brakes and making the car loose, try moving the brake bias to the front first. We usually need a front-to-rear percent ratio of 60:40 or 65:35 for most stock cars.
If that does not help, then decrease the rebound in the LR shock and/or increase the compression in the RF shock. A common fix to a car that was tight on entry used to be to increase the LR shock rebound rate to pull load off the LR corner as the car entered the turn. This would theoretically loosen the car. While that would probably help the situation, it is only a crutch. Look for the real problem first before taking drastic measures with your shocks.
When our moment center is...
When our moment center is located to the left of centerline, the moment arm is longer and the front end will tend to roll more. As we move the MC to the right, the moment arm will become shorter, and the front end will become stiffer and roll less.
4. MOMENT CENTER DESIGN
The front moment center location plays a huge role in the front end's tendencies. The MC should always be somewhere close to the centerline that is midway between the tire contact patches. The farther left the MC is located, the more efficient the front end will be and the more inclined it will be to roll. If the MC is farther to the right of the centerline, then the front end will be stiffer and less likely to roll. Low-banked tracks require a location more to the left and higher-banked tracks require a setup with a MC more to the right of centerline.
The center of gravity height also influences where the MC should be located. Cars with a lower CG should have a MC that ends up farther to the left side of the scale than that of cars with a higher CG.
We should divide the turn...
We should divide the turn into three phases or segments in order to analyze the handling. The middle phase is most important to overall track performance. Entry and exit performance helps us pass cars on the racetrack.
5. BASIC HANDLING PROBLEMS
A tight/loose condition is evident when a car appears to be loose when in fact it is tight. This condition is very hard to detect from a driver's perspective. The car feels loose right at midturn and off the corner. Sometimes the car is tight and the driver has to turn the steering wheel far enough to get the car to turn.
Because the front tires generate more traction with a greater angle of attack, the driver is actually putting more traction into the front end by turning the wheels. The once-tight condition now switches to loose as the front gains grip from excess steering angle. This happens very quickly and the rear end snaps loose as the throttle is applied. All the driver knows is that the car is loose. To correct this, we have to fix the tight condition so that less steering input is required. This malady is more common than most racers know.
Tight in the Middle-The Car Won't Turn
This is the A-one complaint for most ill-handling stock cars on dirt or asphalt. The problem usually is a result of the following: 1) poor front-end geometry, involving moment center location and steering geometry; 2) a rear end that is pointed to the left of centerline; and 3) the wrong choice of springs, weight distribution, and rear moment center height.
Generally speaking, to help the car turn better, we want to first reduce or eliminate Ackermann effect in the steering system. We need to position our moment center so that the dynamics of the front suspension system makes the LF tire work harder. As we move the MC more to the left, the front end becomes more efficient and turns better, to a point. We have covered where the MC should be located for dirt and asphalt racing in past articles.
Finally, we need to balance the spring setup. What we have discovered is that the front roll stiffness exceeds the rear roll stiffness in a tight setup. A front suspension system that is stiffer than the rear end will produce an unbalanced car that is tight and won't turn the corner. An excessively stiff RF spring and/or a RR spring that is too soft can help cause this imbalance.
When we're trying to make...
When we're trying to make a pass, it is critical that the car turns when we're coming off the turn. Getting good forward bite and being able to turn under the outside car helps us complete the pass.
Turn Entry and Exit Handling
The entry to and exit from the middle are affected by transitional components in the car. Transitional components include the shocks, rear roll steer, brakes, rear steer, camber change, rear stagger, and the "Anti's" (dive and squat).
We usually want to work with corner entry first. Problems associated with entry can carry on into midturn. Many times, a driver may feel very uncomfortable with entering a turn. The car just does not take a good set as he or she begins to brake and turn left. This feeling causes the driver to back off earlier and to not go as deep into the corner as other cars. This problem can be associated with how we arrange our springs.
At higher-banked tracks, say 12 degrees or more, a setup utilizing a stiffer right-front spring and/or shock compression will tend to load the crossweight percentage on entry as the car is braking and starting to turn left. That is because the LF will dive more than the RF on braking, momentarily generating added load to the RF and LR tires. This elevated crossweight percentage, or added bite, feels good to the driver, who knows that the rear end will stay under the car.
At flatter racetracks, especially on dirt, we have a very different cause and solution to the problem. When we apply the brakes going into the corner on a flat surface, we want the car to begin to roll in the same direction as it ultimately will in the middle of the turn. If we set up the car with a stiffer RF spring, the car will do a sort of flip-flop, first starting to roll left when braking and diving (due to the softer LF spring) and then rolling to the right as we continue to roll through midturn. This is sometimes visible to the observer watching from outside the car.
The solution is to run a LF spring that is stiffer than the RF spring. As we brake into the corner, the RF spring will compress more than the LF spring and the car will begin to roll to the right. As the car continues on to midturn, it will continue to roll more to the right and the transition will be much smoother, enabling deeper corner entry.
Spring split has such a profound...
Spring split has such a profound effect on the rear roll angle because of the direction of the resultant force in the rear suspension. Softer right-rear springs over the left-rear spring causes additional roll angle. A softer left-rear spring reduces the rear roll angle and makes the rear stiffer.
6. SHOCK DESIGN BASICS
For a car to be fast, the driver must have a good feel for what the car is doing. A soft ride that feels sloppy does nothing to give a driver confidence in knowing what the car will do next.
Many racers think that increased compression in the shocks should help this problem, but too often that has an opposite effect. The car may indeed need more compression in the shocks, but the rebound should always be higher than the compression to control excess body sway and roll. In most cases, just increasing the rebound resistance will solve the problem.
Again, with the big bar and soft spring setups, excess movement of the suspension can be a problem. Higher rebound rates are essential for controlling suspension movement. Many of the tech support persons who work for short-track shock companies have worked out shock valving solutions for those who want to experiment with the BBSS setups.
For dirt cars, where a lot of vertical movement is desirable to get more weight transfer on dry-slick racetracks, reduced compression and rebound may be helpful, and a lot of movement should be expected. Of course, this depends on the track conditions. The tighter the track, meaning the more grip, the more we need to control the suspension movement by stiffening the shock rates.
The angle of the trailing...
The angle of the trailing links can be used to cause rear steer to the left upon acceleration as the cahssis squats. We need to be cautious with this effect, as overdoing it will cause excess rear steer to the right at mid-turn as the left side of the car is raised.
7. POOR FORWARD BITE
]At the higher-banked racetracks, we usually do not have a problem with traction off the corners because of the downforce created by the banking. On many flatter tracks, it may seem like we can never get enough bite.
Bite can be enhanced by several methods: a) use of a softer RR spring (only 10-15 pounds on asphalt and more on dirt); b) use of a pull bar or lift arm to reduce the "shock" from the initial application of power to the rear tires when we get back into the throttle; c) introducing rear steer as the car squats on exit. This is done using the rear trailing arm angles and/or a height differential of the links.
On a three-link rear suspension, a higher trailing arm angle (front pivot mounted higher) on the left trailing arm will push the LR back as the car squats on exit, providing rear steer to the left and promoting forward bite.
On a four-bar rear suspension, the arms can be positioned to provide rear steer similar to that of the three-link as the car squats. This is usually done by mounting the front of the links in the higher holes on the left side. With the use of a lift bar, this effect could be reversed, causing rear steer to the right.
8. PROPER GEARING/REAREND PROBLEMS
A car that is sluggish off the corner and tends to be a rocket at the end of the straightaway may be geared incorrectly. The place to accelerate quickly is not at the end, but at the beginning of the straightaway for several reasons.
Using a lower gear to get off the corners will produce more increase in mph in the first half of the straight than a higher gear will produce in the last half of the straight. We can pass much better and more safely coming off a corner than on entry. Diving in under a competitor can have some very negative consequences.
We must properly maintain our rearend. The wrong tension springs in a locker rearend or springs that have lost their tension will cause all kinds of setup problems as the wheels lock up erratically. A mid-season inspection and maintenance on our rearend will help us avoid mid- to late-season problems.
Sliders such as these must...
Sliders such as these must be inspected and maintained often to prevent corrosion. If these parts do not move freely, then the setup will be off and the handling will be hard to nail down.
All race cars need maintenance. Ball joints, Heim joints, sliders, brakes, the cooling system, the fuel system, and any other system that we rely on must be inspected. Dirt cars are especially prone to corrosion problems due to the fact that the cars are constantly washed down and cleaned after every event.
The coilover eliminators must be maintained, sometimes on a week-to-week basis. Shocks must be inspected often. You should take them off and cycle them by hand through the complete range of motion. Broken valving and air intrusion can be detected by doing this, and handling problems associated with bad shocks can be avoided.
Remember that you need to...
Remember that you need to run the correct stagger based on the radius of your track. Problems with tightness in the middle (when using a spool rear differential) or tightness off the corners (when using a locker differential) can be caused by insufficient stagger. The formula shown is for determining the correct stagger.
10. DRIVING STYLE
Last, but certainly not least, is a short discussion about driving. Many drivers are "never wrong," so they think. And trying to convince a parent that their little darling isn't perfect can be very frustrating for a consultant or crew chief. But sometimes getting ahead is only a matter of helping the driver to understand the track. The best driving line might be in a different place from what feels fast to the driver. The stopwatch and passing performance depend on driving the correct line, not what feels fast to the driver.
I had a recent personal experience with this phenomenon. A driver who dives into the corner low and then pinches the middle does the tires no good and will end up losing a lot of ground to drivers who are more disciplined and drive in wider to increase the radius of the middle of the turn. Just watching the progression tells the whole story.
A car moves up on another car for position, gets under it down the straightaway, and then pinches the corner as the outside car moves on past midturn, where the whole scenario repeats itself until the inside car wears its stuff out.
One of the most frustrating things I have seen is when a driver has a fast car, gets up under another car and, as the car approaches the turn, allows the outside car to have the preferred line. It's as if the passing (inside) driver is afraid to move the other car out.
When we have the inside line, we have to imagine that the other car is not there. The driver of that car is on his or her own at that point and must live with wherever we decide to drive. Taking the correct line forces the outside driver to end up running too high and he or she will need to back off in order to enter and exit the turn without crashing. The pass will then be completed.
We hope that these tips will cause you to rethink certain aspects of your approach to handling problems. If you are in the points lead or in close range to a good points position, go over some of these items and make sure everything is where it should be. Then push on to the end of the season and make every effort to run as hard as you can. It would be nice to look back this winter on a successful season in order to look forward to next year's racing.