Ford 2011 Fiesta Owner's Manual page 221

Tires, Wheels and Loading
When inflating your tires
When putting air into your tires (such as at a gas station or in your
garage), the tire pressure monitoring system may not respond
immediately to the air added to your tires.
It may take up to two minutes of driving over 20 mph (32 km/h) for the
light to turn off after you have filled your tires to the recommended
inflation pressure.
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
overnight with the outside temperature significantly lower than the
daytime temperature, the tire pressure may decrease approximately 3 psi
(21 kPa) for a drop of 30°F (17°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
light 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 original equipment tires on your vehicle have an all-weather tread
design to provide traction, handling and braking performance in
year-round driving. You may install snow tires for improved traction
when driving in areas with sustained periods of snow or icy driving
conditions.
220
2011 Fiesta (fie)
Owners Guide, 3rd Printing
USA (fus)