Hugh---You can count the threads per inch on the tie rod to give an
approximate on the amount the wheel will move, as the adjustment is
screwed in or out. (A chalk mark helps here) However, if you move the
adjustment rod one full turn, and if it's 1/16", this is a LOT of
change. Note that each wheel pivots from a center, and changing each one
by a sixteenth should give a total alignment change of a quarter inch
front to back on that pair of wheels.
A handy gauge can be made up from three pieces of 2"x2" wood. Two pieces
about a foot long attached to a 'handle' about five feet long. It will
resemble the capital letter "F" when glued and screwed together. Without
getting into full chassis alignment here, the amount of toe is relative
on each end of the car. Using a pocket scale, or something that measures
to 1/32", one can measure the difference between the front and back of
the tires at the wheel centerline, as the "gauge" is moved from back to
front on a pair. Being careful to not pick up a bump in the sidewall,
and assuming a reasonably straight pair of wheels, it's possible to get
very close to what you want the toe to be.
This is handy if you autocross the car, and want to return to a street
setting without the time and expense of a professional alignment. I can
say that my tires wear straight doing it this way. It also works well
for the rears, when starting from a known true chassis alignment.
String and jack stands works well here, but that's another story.
Dick
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