Vehicles are designed to have zero or minimum toe change and side scuff when:
1.     The vehicle is at correct ride height statically and dynamically.
2.    All related parts are operating within normal wear tolerances, and
3.    The  steering  and  suspension  components  can operate at the proper alignment angles.

Countless books and service guides have been produced to show how to check all mechanical components and ride height quickly and accurately, so there Is no need to go Into that here.  But, If you don't know how to read all the angles accurately, and consistently correct (and that goes for S.A.I. (Steering Axis Inclination) and turning radius). touch  base  with  your  alignment  equipment  service  training representative because that's their job.  And if they say:  "Don't worry about S.A.I. and turning radius because they are both non-adjustable angles and you can't adjust them anyway." It's because they either don't know how to get consistent accurate reading, or simply don't know how to read them. Either way, get someone who can, because both readings are critical to proper diagnosis and solving the type of tire wear we are talking about.

Once you've read and recorded all the alignment angles and the riding height, then check all the steering and suspension parts for wear and damage. Also inspect the frame cross members and body for signs of damage, both present or repaired.  Incorrectly repaired damage Is a common cause of various handling and tire wear problems on today's cars  because  even  though  the  adjustable  angles  may be  okay statically, they may not operate at the proper angle dynamically and this Is where S.A.I. and turning radius come In to the picture.  If these two angles are not correct, there Is almost always a bent component
involved.
For example:   control arms, spindle and support, ball joint stud, MacPherson Strut shock rod, strut tower and mounting supports, frame or cross member, steering arm, pitman arm and steering box support. Idler arm and frame support, rack and pinion housing support.  You've really got to take a close look at these components when checking for damage. Often, the only way is to compare from side to side and/or make measurements from the component to the floor, to the wheel, to the mainframe.   The main clue to a problem here Is that physical damage will usually result In unequal S.A.I. and turning radius from side to side.  Even though you may not have the specs (and unfortunately some leading manufacturers do not give us
this Information), check them anyway because they should normally be within one degree of each other side to side.  And since It's unlikely both sides of the vehicle will suffer equal and similar damage, a  difference means a problem  If the readings are equal, there is not likely a problem!