2011 Chevrolet Express 1500 Cargo Owner's Manual - Page 339

Vehicle Care Some commercial truck tires, including Goodyear LT225/75R16 G949 RSA and Goodyear LT225/ 75R16 G933 RSD, may not have treadwear indicators. If the tires do not have treadwear indicators, replace the tires when the tread depth is down to 3.2 mm (1/8 in) for the front tires, or 1.6 mm (1/16 in) for the rear tires. See Tire Inspection on page 10‑66 and Tire Rotation on page 10‑66 for additional information. The rubber in tires ages over time. This also applies to the spare tire, if the vehicle has one, even if it is never used. Multiple conditions including temperatures, loading conditions, and inflation pressure maintenance affect how fast aging takes place. Tires will typically need to be replaced due to wear before they may need to be replaced due to age. Consult the tire manufacturer for more information on when tires should be replaced. 10-69 Buying New Tires GM has developed and matched specific tires for the vehicle. The original equipment tires installed were designed to meet General Motors Tire Performance Criteria Specification (TPC Spec) system rating. When replacement tires are needed, GM strongly recommends buying tires with the same TPC Spec rating. GM's exclusive TPC Spec system considers over a dozen critical specifications that impact the overall performance of the vehicle, including brake system performance, ride and handling, traction control, and tire pressure monitoring performance. GM's TPC Spec number is molded onto the tire's sidewall near the tire size. If the tires have an all‐season tread design, the TPC Spec number will be followed by MS for mud and snow. See Tire Sidewall Labeling on page 10‑53 for additional information. Vehicle Storage Tires age when stored normally mounted on a parked vehicle. Park a vehicle that will be stored for at least a month in a cool, dry, clean area away from direct sunlight to slow aging. This area should be free of grease, gasoline or other substances that can deteriorate rubber. Parking for an extended period can cause flat spots on the tires that may result in vibrations while driving. When storing a vehicle for at least a month, remove the tires or raise the vehicle to reduce the weight from the tires.