Caster Angle Determination - "G" Series

1. With vehicle on level surface and using bubble protractor or inclinometer, determine frame angle. Determine caster angle. To determine actual (corrected) caster angle with various frame angles and caster angle readings from alignment equipment, one of these rules will apply:
   • A "down in rear" frame angle must be subtracted from a positive caster angle reading. See Fig 1 , Example A.
   • An "up in rear" frame angle must be added to positive caster angle reading. See Fig 1 , Example B.
   • A "down in rear" frame angle must be added to a negative caster angle reading. See Fig 1 , Example C.
   • An "up in rear" frame angle must be subtracted from a negative caster angle reading. See Fig 1 , Example D.
2. Dimension "BC" is measured 90 degrees from the lower surface of the crossmember assembly to the inboard rear corner of the jounce bumper bracket. See Fig 1 , View A. Using dimension "BC" and the WHEEL ALIGNMENT SPECIFICATIONS  table, determine recommended caster angle.
3. If actual (corrected) caster angle (step 2) does not correspond to a recommended caster angle (step 3) within F1 degree, change shims to bring actual (corrected) caster angle in line with recommended caster angle.

Fig 1: Determining Caster Angle (Typical)

Courtesy of GENERAL MOTORS CORP.