Step 7. Right Side Tire Contact Patch Alignment
A laser is the very best way to do your alignment because it is so accurate and easy to re
Once the front wheels have been adjusted to point straight ahead and parallel to the centerline, we need to align the right side tire contact patches. We do this by using our laser systems as described in the user manuals for each system.
Adjust the panhard or J-bar length so that the right side tire contract patches are inline, or if your desire is to offset these, set the desired amount. This means that we will either have both right side tires lined up or at least know what our offset is. For stock classes using rear suspensions that are not adjustable, you will need to run different offset wheels to achieve right side tire alignment.
When using either the string method or the lasers at hub height, we need to compensate for the camber of the wheels, which moves the tire contact patches out. At the hub height, if we line up the tire sidewalls, the RF tire contact patch will be outside that line due to the negative camber present in the RF wheel. The rear wheel may also have camber due to a cambered rearend or just the stagger.
Look at the chart to estimate how much to compensate for the cambers. Subtract the compensation amount from the offset read at the wheels to find how far from the string the wheels need to be in order to line up the right side tire contact patches.
As we adjust the rearend side to side, there is a possibility that the rearend alignment will change as the rearend moves laterally. That is why we do the right side alignment first. We will now need to check to make sure the rearend is perpendicular to the chassis centerline and if not, adjust it.
Step 8. Rearend Alignment
Once the right side tire contact patch alignment has been done, we can then square the rearend. The rear end should always be set perpendicular to the centerline of the car. We do this with the strings by creating a line that is perpendicular to the centerline we have already established. Using a simple 3-4-5 right triangle with the lengths doubled, we can measure off the centerline to establish our line to measure to the rearend.
When using the laser systems, follow the manufacturer's guidelines for doing that. The lasers will accurately measure the alignment referencing the chassis centerline.
Step 9. Setting Front Toe
Many teams use solid links to position the rearend or front suspension control arms at the
The last step in the alignment process it to set the static toe at the front wheels. We can use toe plates to do this or the laser systems. Remember to be careful and accurate and do the measurements several times to be sure of the numbers. I usually just adjust the left side tie rod to set toe and leave the right side alone. You can use both if you want.
Roll the car forward and back about 5 feet and recheck the toe setting. As the car settles, the overall measurements may change, but the differences should remain the same. Remember that for toe-out, the front measurement will always be more than the rear measurement on the toe plates. If you are using a string or laser to check your toe-out, the opposite is true. The front measurement from the laser/string would be less than the rear measurement. I know one crew chief/car owner that got this backwards too many times.
Step 10. Drive Line Alignment
An additional step you might consider is to align the drive line components. This means the transmission tail shaft—to driveshaft—to pinion shaft angles. The driveshaft needs some angle in relation to the tranny and pinion in order to load and rotate the needle bearings in the universal joints, but this angle can be small, at 1 to 2 degrees.
Also, the angles at each end of the driveshaft need to be equal and opposite. This provides good harmonics and if this is out of range, serious vibrations and failure of components can result.
Also remember that some cars are constructed so that from a top view, there is miss-alignment between the transmission and the pinion, especially for offset chassis. If this is enough to provide the equal and opposite angles we need, then the side view angles can be zero. The tranny, driveshaft and pinion can therefore be inline.
There are even systems out there that help you measure your driveshaft alignment laterally
This whole process of aligning your car should only take about an hour or two if there are several team members helping. That is very little effort expended to make sure your car will track correctly and that misalignment will not interfere with your car's performance. Even if the process took a whole day, your performance improvement will make the time spent well worthwhile.
Repeat this entire process as often as you feel necessary and especially after kissing the wall or being involved in contact with another car or being involved in a crash. Maintain your intended chassis ride heights once you have performed the chassis alignment process. Once you are convinced that your car is aligned, you can then concentrate on the other important aspects of your chassis setup.