Whenever an off-vehicle wheel balancer is used, whether for measuring wheel runout or for balancing, the wheel must be installed on the balancer using a cone through the back side of the wheel's center pilot hole. Locating in any other manner could result in erroneous measurements.
Most wheel balancing machines are designed for back coning. Some wheel balancers, however, are designed to front cone light duty truck wheels with large center pilot holes. Comments have been received of this being done to 16 x 6.5 inch, 8 bolt, code "AA" wheels, P/N 14035374. The pilot hole's front side on such wheels is not a controlled surface. Front coning on this surface could cause wheels to be incorrectly measured as having excessive runout, or it could result in an inaccurate balance.
If your wheel balancer calls for front coning, consult the equipment manufacturer. Minor modificafions can usually be made to allow back coning.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.