2007 Chevrolet Cobalt Owner's Manual - Page 344

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. If your vehicle has 215/45R18 size tires, they will require inflation pressure adjustment when driving your vehicle at speeds of 100 mph (160 km/h) or higher. Set the cold tire inflation pressure to 35 psi (241 kPa) for the front and rear tires, when operating your vehicle at high-speed conditions. When you end high-speed driving, return the tires to the cold inflation pressure shown on the Tire and Loading Information label. See Loading Your Vehicle on page 253 and Inflation - Tire Pressure on page 342. 344