2009 Pontiac G8 Owner's Manual - Page 255

Vehicle Service and Care 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. 9-51 High-Speed Operation { CAUTION Driving at high speeds, 100 mph (160 km/h) or higher, puts an additional strain on tires. Sustained high-speed driving causes excessive heat build up and can cause sudden tire failure. You could have a crash and you or others could be killed. Some high-speed rated tires require inflation pressure adjustment for high speed operation. When speed limits and road conditions are such that a vehicle can be driven at high speeds, make sure the tires are rated for high speed operation, in excellent condition, and set to the correct cold tire inflation pressure for the vehicle load. Vehicles with P245/45R18 96V, 245/45R18 96V, or 245/40R19 94W size tires, require inflation pressure adjustment when driving the vehicle at speeds of 100 mph (160 km/h) or higher. Use the following chart to determine the cold tire inflation pressure when operating the vehicle under high-speed conditions.