The chart shows how much each...
The chart shows how much each wheel turns related to toe. For an 86-inch circumference tire, a 111/42-inch movement of the string at the plate when we turn the wheel results in 0.342 inch of toe, or wheel movement related to toe. Subtract the results for each wheel and you will have the amount of toe gain or loss due to steering input.
A simple, yet accurate way to measure Ackermann is to use a laser or string to project the alignment of the wheel/tire out in front of the car. If you place targets in front of the tires at a distance of exactly 10 feet from the center of the hub, you can mark where the tires point at straight-ahead and then at wheels-turned positions.
A select few racers discovered the problem and corrected it with different length steering arms. They dominated racing during that period because their cars turned better than the competition. Today, with a better understanding of Ackermann and the amounts needed by the cars, we can measure our Ackermann and correctly adjust any excess toe steering quickly and easily. Remember, no amount of chassis setup adjustment will overcome excess Ackermann effect and the loss of front grip associated with it.
How to Test For Ackermann Effect
Here is a simple, easy test: First, scribe a line on each front tire around the entire circumference at about the middle of the tread. Use a toe bar with adjustable width pointers and measure the toe with the wheels pointed straight ahead by measuring the front and rear width on the scribe line and subtracting the widths.
By using a precise laser alignment...
By using a precise laser alignment system, the amount of steering in each front wheel can be measured to determine the presence of either Ackermann or Reverse Ackermann. The movement in inches of the laser dot on the target is translated into exact toe gain or loss.
Turn your steering wheel the same amount as the driver would steer at mid-turn, and then recheck your toe using the same method. You will be able to record the true amount of gain (Ackermann) or loss (Reverse Ackermann) in toe. Toe plates that read in degrees are not accurate enough for this purpose and may slip as the wheels are turned.
The use of a quality laser alignment system will do the same thing as using strings or toe bars, only more accurately. Given the importance of having correct toe gain from steering input, investing in a laser system would be considered a reasonable investment that would provide a sizable return if a problem were present and eliminated.
If your car gains or loses toe, there are a couple of ways to correct the situation. You can adjust the length of your steering arms to compensate for Ackermann effect. Lengthening the left steering arm will reduce the amount that the wheel turns, which reduces Ackermann effect. The opposite is true for the right steering arm-we would need to shorten it in order to reduce Ackermann. We can also change our drag link to move the inner ends of the tie rods forward to reduce Ackermann, or rearward to reduce Reverse Ackermann effect.
This spindle has a slotted...
This spindle has a slotted hole where the tie rod end mounts to the steering arm. This allows the team to adjust the length of the steering arm to control the amount of Ackermann effect.
If your spindles were not designed for your steering system, change to the correct spindle design and possibly have some lightweight spindles fabricated to the exact specifications as the correct spindles.
Caution: Do not make spindle changes without knowing how the change will affect your moment-center location. You may be making a positive change in your steering system and a negative change in the moment-center design.
Make sure you know how much each of your tires is steering, and balance your setup so that both front tires are working together to steer your car. A good-turning race car is one that will have more turning power and is therefore more capable of running up front and winning races.