The amount of Ackermann in...
The amount of Ackermann in our rack-and-pinion steering system can be regulated by moving the rack forward or backward in the car. This adjusts the top-view angles of the tie rods to change the amount of spread that occurs between the ends of the steering arms as we steer the car.
This is the most practical way to adjust Ackermann in a dirt Late Model due to the fact that we steer both ways on dirt. This solution eliminates Ackermann in both steering directions and does not create reverse Ackermann.
A common solution for asphalt cars, and one that is not recommended for dirt cars by virtue of them having to steer both ways, is to change the lengths of the steering arms so that each spindle turns the same number of degrees as the other. If we have Ackermann present in our car, we can lengthen the left steering arm to slow down that spindle and/or shorten the right steering arm to speed up that spindle. Again, this only works to reduce Ackermann when we steer to the left.
In a stock-designed drag-link system, we can move the drag link forward to reduce the amount of Ackermann for dirt or asphalt cars. On asphalt, the same quick fix can be used by lengthening or shortening the steering arms, as discussed earlier with the rack-and-pinion systems.
3. Rear 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 the alignment issues have been resolved. The rear end should be at right angles to the chassis centerline, and the right-side tire contact patches should be in line.
If the rear end is misaligned, with the wheels pointed left of centerline, then the car will be very tight and won't turn well. This is another condition that will override proper MC design, a balanced setup, and minimal Ackermann. If not remedied, this problem will ruin an otherwise great race car.
Some spindles have a slotted...
Some spindles have a slotted hole in the left steering arm. This allows adjustments to the length of the steering arm in order to reduce Ackermann effect.
4. An Unbalanced Setup A tight car can also be caused by a tight setup, a result of an unbalanced setup or running the wrong crossweight percentage. Tire temperatures reveal a lot about the setup and where we need to look to fix the balance problem.
If the average temperatures of the front tires are higher than the average temperatures of the rear tires, then the car is probably tight and may have too much crossweight. The car should respond to a reduction in crossweight, but this adjustment does not necessarily fix a setup that is dynamically unbalanced.
In the case of an unbalanced setup causing a tight condition, the rear of the car will tend to roll more than the front. There are several things we can do to help bring a better balance to the car. We can raise the Panhard bar to raise the rear roll center, which will cause the rear suspension to stiffen and roll less.
We can change the amount of...
We can change the amount of Ackermann in our drag-link steering system in a way similar to how we adjust the rack-and-pinion system. If we move the drag link forward in the car, we will take top-view angle out of the tie rods and reduce the amount of Ackermann in this system.
We can reduce or eliminate the rear spring-rate split if we use a softer right-rear spring. That too will reduce the rear roll angle. If we are running on a banked track of 12 degrees or more, we can also increase the rate of the RR spring over the LR spring rate to reduce the rear roll angle.
At the front end, we can do a few things to cause the front to be softer and tend to roll more in order to try to match the desire of the rear. We can soften the RF spring and stiffen the LF spring to make them equal, or even install a stiffer LF spring than the RF spring on flatter tracks. The stiff LF spring setup does not work well on tracks banked over 10 degrees. Using a smaller sway bar increases the front roll angle, but not very much. We mostly use the sway bar to tune for traction off the corners with conventional setups.
5. Crossweight Percentage Crossweight percentage is defined in circle track racing as the sum of the RF and LR wheel weights divided by the total vehicle weight. If all else is correct, such as alignment, moment center location, dynamic balance, camber change, and so on, and the car is still not neutral, then the crossweight percentage is probably wrong for the weight distribution in the car. Reduce the percentage of crossweight for a tight car and increase the crossweight percentage for a loose car.
A balanced car is evidenced by tire temperature readings. The front and rear averages should be close to the same (add the front two tire temperatures and compare to the rear two tire temperatures), and each of the side tires should have nearly the same temperature front to rear. For example: LF + RF = LR + RR, LF = LR and RF = RR. Work to get these temperatures correct and then fine-tune the handling balance with the crossweight percentage.