There was a technical service bulletin issued to dealerships early last fall about this condition. There has also been an update to factory build to install a retainer to keep the liner back away from the tire. (Of course this assumes that your car doesn't have an alignment issue, just the clearance issue.) Here is the latest version, with fix and picture:
Originally Posted by GM TSB(edited by Small Dealer)
Subject: Rubbing Noise From Rear of Vehicle (Install Retainers to Wheel Liner)
Condition
Some customers may comment on a rubbing noise from the rear of the vehicle.
Cause
This condition may be caused by the inner wheel liner making contact with the tire .
Correction
Install new retainers in the left and right inner wheel liner following the procedure below.
1) Remove the rear tire and wheel.
2) Make a measurement from the corner 90 mm (3 ˝ in). The second measurement will be to measure up 40 mm (1 ˝ in). Refer to the illustration.
3) Drill a hole through the plastic wheel liner and the sheet metal using a 6 mm (15/64 in) drill bit.
4) Drill the hole larger in the plastic liner using a 8 mm (19/64 in) drill bit to eliminate contact with the retainer.
5) Apply SuperLubeŽ with PTFE to the end of the retainer and install the new retainer. You must push firmly on the retainer to fully seat it.
6) Install the wheel and tire.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these 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 your GM dealer for information on whether your vehicle may benefit from the information.