Prior to checking and adjusting the angles of alignment,
the steering and suspension system should be checked
thoroughly to ensure that the vehicle can be aligned successfully.

Curb Height and Weight

The vehicle should be checked to ensure that the height is correct
at the front and rear and is even from side to side.  The fuel tank
should be full, and any normal load that the driver would carry should
be in the vehicle (ie. toolboxes in trucks).  If the vehicle is equipped
with front torsion bars, these should be adjusted to obtain the factory
specified front height.

Inspections
 

STEERING AND SUSPENSION

Once the inspections have been made, then the vehicle can be
set up on the alignment rack, and the angles can be measured
and adjusted as necessary.

Alignment Measuring Equipment

Magnetic Gauge

Older alignment systems used a magnetic gauge which attached
to the front wheel spindle, and the angles were measured using
a "bubble gauge" built into the caster/camber gauge.  This is
still often used during suspension repairs to get a quick reading
adjustment prior to replacing the wheels after strut replacement.
 

Computerized Alignment

Because of the need to perform 4 wheel alignments, today's
Technicians use a computerized system which has
an alignment head attached to each of the four wheels.
Measurements are made using infrared light beams,
resulting in very high accuracy.  Many systems use
wireless heads that send the readings back to the
computer console.