Ford 2009 Expedition Owner's Manual page 268

Tires, Wheels and Loading
How temperature affects your tire pressure
The Tire Pressure Monitoring System (TPMS) monitors tire pressure in
each pneumatic tire. While driving in a normal manner, a typical
passenger tire inflation pressure may increase approximately 2 to 4 psi
(14 to 28 kPa) from a cold start situation. If the vehicle is stationary
over night with the outside temperature significantly lower than the
daytime temperature, the tire pressure may decrease approximately 3 psi
(20.7 kPa) for a drop of 30° F (16.6°C) in ambient temperature. This
lower pressure value may be detected by the TPMS as being significantly
lower than the recommended inflation pressure and activate the TPMS
warning for low tire pressure. If the low tire pressure warning light is
ON, visually check each tire to verify that no tire is flat. (If one or more
tires are flat, repair as necessary.) Check air pressure in the road tires. If
any tire is under-inflated, carefully drive the vehicle to the nearest
location where air can be added to the tires. Inflate all the tires to the
recommended inflation pressure.
SNOW TIRES AND CHAINS
WARNING: Snow tires must be the same size, load index, speed
rating as those originally provided by Ford. Use of any tire or
wheel not recommended by Ford can affect the safety and
performance of your vehicle, which could result in an increased risk of
loss of vehicle control, vehicle rollover, personal injury and death.
Additionally, the use of non-recommended tires and wheels could
cause steering, suspension, axle or transfer case/power transfer unit
failure.
The tires on your vehicle have all weather treads to provide traction in
rain and snow. However, in some climates, you may need to use snow
tires and chains. If you need to use chains, it is recommended that steel
wheels (of the same size and specifications) be used, as chains may chip
aluminum wheels.
Follow these guidelines when using snow tires and chains:
• Use only cable type chains or chains offered by Ford as an accessory
or equivalent. Other conventional link type chains may contact and
cause damage to the vehicle's wheel house and/or body.
• Do not install chains on the front wheels. Chains on the front wheels
may interfere with suspension components.
• Chains are not recommended for use on the P275/55R20 tire.
• Install chains securely, verifying that the chains do not touch any
wiring, brake lines or fuel lines.
268
2009 Expedition (exd)
Owners Guide, 1st Printing
USA (fus)