Good handling is often thought to be a car that is neutral as it runs through the entry, middle, and exit of the corner. While that may be fine as a goal, what we really want is a balanced and neutral setup that will stay consistent throughout the race. When the car is not neutral, there are some good, and some not so good, ways to make it neutral. Here, we will examine the problems associated with a poor-handling car and some logical steps to take to find the most balanced setup.
A poor-handling car is defined as one that is either loose (rear has less traction than the front) or tight (front has less traction than the rear), known by road racers as oversteer and understeer. For our purposes, we'll stick to the circle track lingo. The tight or loose condition can be in either of the three phases of the turns: entry, middle, or exit, or any mix of the three. The cure must address where the car isn't handling and ideally not affect where the car is good.
We will look at each phase of the corner and present handling fixes based on what the car is doing at each point. We will start with the mid-turn handling because problems that affect the car in the middle can also affect the entry and exit. If we can get the car good in the middle, we might have solved some of the entry and exit problems. Usually, improved mid-turn handling offers the most gain in overall track performance and that is why we start there and make sure that segment remains good if we need to make changes to improve the other phases.
Mid-turn Handling Mid-turn handling problems can be caused by a car that is either tight or loose. By far, the most common handling malady is when the car will not turn. This can be caused by several different conditions, or a combination of several. We will need to go through a checklist to eliminate some familiar problems. The following is, in order of significance, a checklist of things that can make the car not want to turn.
1. Front Moment CenterLocation-The front moment center (MC) location plays a huge role in how the front end wants to work. The MC should always be somewhere close to the centerline that is midway between the tire contact patches. The farther to the left the MC is located, the more the front end will want to roll. The farther to the right of the centerline, the less the front end will want to roll. Low-banked tracks require a location more to the left and higher-banked tracks are best setup with a MC more to the right of the centerline.
The center of gravity (CG) height influences where the MC should be located. Cars with a lower CG should have a MC that ends up farther to the left than would cars with a higher CG.
2. Excess Ackermann-In the front end geometry related to steering, 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 to the left. The opposite of Ackermann is called Reverse-Ackermann. That is an effect that causes a decrease in the amount of toe 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 Ackermann designed into our cars, intentionally 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 help the situation. We must eliminate most of the Ackermann. The fix is different for the two most common types of steering systems we find in circle track stock cars.