The tire contact patch is...
The tire contact patch is offset from the center of the wheel at hub height when we add camber to a wheel. The chart shows how far offset the contact patch center is related to the wheel center at hub height. This is important to know when stringing a car at hub height which is a common practice. If we string along the rear tire bulge to the front tire, the front tire-to-string should be a gap equal to the chart offsets. If the rear and front wheels have camber, then subtract the rear offset from the front offset and make your front tire gap that dimension.
A greater measurement for the left tire indicates Ackermann (gain in toe-out) and a greater measurement for the right tire indicates Reverse Ackermann (loss of toe-out). A 1 inch difference equals about a inch of Ackermann or added/loss of toe for an 85 inch circumference tire. So, if you can get your differences to inch or less, where the left side is more, you should be good to go. A recent car we checked had a three inch difference, or almost inch of added toe in the turns.
Step 7 Setting Front Toe 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. Adjust the left-side tie rod to set your toe. Leave the right side alone.
Roll the car forward and back about five 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 who got this backwards too many times.
Conclusion This whole process of aligning your car should only take about an hour or two if there are several team members helping. That's 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 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.