2004 GMC Sierra 1500 Pickup Owner's Manual - Page 485

When to Check Check your tires once a month or more. Also, check the tire pressure of the spare tire. Dual Tire Operation When the vehicle is new, or whenever a wheel, wheel bolt or wheel nut is replaced, check the wheel nut torque after 100, 1,000 and 6,000 miles (160, 1 600 and 10 000 km) of driving. For proper torque and wheel nut tightening information, see "Removing the Flat Tire and Installing the Spare Tire" in the index. The outer tire on a dual wheel setup generally wears faster than the inner tire. Your tires will wear more evenly and last longer if you rotate the tires periodically. See "Tire Inspection and Rotation" earlier in this section. Also see "Scheduled Maintenance Services" in the Index for scheduled rotation intervals How to Check Use a good quality pocket-type gage to check tire pressure. You can't tell if your tires are properly inflated simply by looking at them. Radial tires may look properly inflated even when they're underinflated. Check the tire's inflation pressure when the tires are cold. cold means your vehicle has been sitting for at least three hours or driven no more than 1 mile (1.6 km). Remove the valve cap from the tire valve stem. Press the tire gage firmly onto the valve to get a pressure measurement. If the cold tire inflation pressure matches the recommended pressure on the tire and loading information label, no further adjustment is necessary. If the pressure is low, add air until you reach the recommended amount. If you overfill the tire, release air by pushing on the metal stem in the center of the tire valve. Recheck the tire pressure with the tire gage. Be sure to put the valve caps back on the valve stems. They help prevent leaks by keeping out dirt and moisture. {CAUTION: If you operate your vehicle with a tire that is badly underinflated, the tire can overheat. An overheated tire can lose air suddenly or catch fire. You or others could be injured. Be sure all tires (including the spare) are properly inflated. See "Tires" and "Inflation - Tire Pressure" in the Index for more information on proper tire inflation. 5-85