Jeep Grand Cherokee Owner's Manual page 455

CAUTION!
After inspecting or adjusting the tire pressure, al-
ways reinstall the valve stem cap. This will prevent
moisture and dirt from entering the valve stem,
which could damage it.
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 mile
(1.6 km) after a three-hour period. The cold tire inflation
pressure must not exceed the maximum inflation pres-
sure 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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