2008 Volvo S40 Owner's Manual - Page 157

NOTE The placards shown indicate inflation pressure for the tires installed on the car at the factory only. Use a tire gauge to check the tire inflation pressure, including the spare, at least once a month and before long trips. You are strongly urged to buy a reliable tire pressure gauge, as automatic service station gauges may be inaccurate. Use the recommended cold inflation pressure for optimum tire performance and wear. Under-inflation or over-inflation may cause uneven treadwear patterns. WARNING Under-inflation is the most common cause of tire failure and may result in severe tire cracking, tread separation, or "blowout," with unexpected loss of vehicle control and increased risk of injury. Under-inflated tires reduce the load carrying capacity of your vehicle. When weather temperature changes occur, tire inflation pressures also change. A 10-degree temperature drop causes a corresponding drop of 1 psi (7 kPa) in inflation pressure. Check your tire pressures frequently and adjust them to the proper pressure, which can be found on the vehicle's tire information placard or certification label. Checking tire pressure Cold tires Inflation pressure should be checked when the tires are cold. The tires are considered to be cold when they have the same temperature as the surrounding (ambient) air. 171 07 Wheels and tires Tire inflation This temperature is normally reached after the car has been parked for at least 3 hours. After driving a distance of approximately 1 mile (1.6 km), the tires are considered to be hot. If you have to drive farther than this distance to pump your tire(s), check and record the tire pressure first and add the appropriate air pressure when you get to the pump.