Chrysler 2008 PT Cruiser - Manual (Page 325)

check tire pressure. Do not make a visual judgement
when determining proper inflation. Radial tires may look
properly inflated even when they are under-inflated.
CAUTION!
After inspecting or adjusting the tire pressure, al-
ways reinstall the valve stem cap (if equipped). This
will prevent moisture and dirt from entering the
valve stem, which could damage the valve stem.
Inflation pressures specified on the placard are always
“cold tire inflation pressure.” Cold tire inflation pressure
is defined as the tire pressure after the vehicle has not
been driven for at least three hours, or driven less than 1
mi (1.6 km) after a three hour period. The cold tire
inflation pressure must not exceed the maximum infla-
tion pressure molded into the tire sidewall.
Check tire pressures more often if subject to a wide range
of outdoor temperatures, as tire pressures vary with
temperature changes.
Tire pressures change by approximately 1 psi (7 kPa) per
12°F (7°C) of air temperature change. Keep this in mind
when checking tire pressure inside a garage, especially in
the Winter.
Example: If garage temperature = 68°F (20°C) and the
outside temperature = 32°F (0°C) then the cold tire
inflation pressure should be increased by 3 psi (21 kPa),
which equals 1 psi (7 kPa) for every 12°F (7°C) for this
outside temperature condition.
Tire pressure may increase from 2 to 6 psi (13 to 40 kPa)
during operation. DO NOT reduce this normal pressure
build up or your tire pressure will be too low.
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