Mercedes-Benz SLR McLaren. Operator's Manual.

Operation
Tires and wheels
Checking tire inflation pressure
Regularly check your tire inflation pressure
at least once a month.
Check and adjust the tire inflation
pressure when the tires are cold. The tires
can be considered cold if the vehicle has
been parked for at least three hours or
driven less than one mile (1.6 km).
If you check the tire inflation pressure
when the tires are warm (the vehicle has
been driven for several miles or sitting less
than three hours), the reading will be
approximately 4 psi (0.3 bar) higher than
the cold reading. This is normal. Do not let
air out to match the specified cold tire inflation
pressure. Otherwise the tire will be
underinflated.
266
Checking tire inflation pressure
manually
Follow the steps below to achieve correct
tire inflation pressure:
Remove the cap from the valve on one
tire.
Firmly press a tire gauge onto the
valve.
Read tire inflation pressure on tire
gauge and check against the recommended
tire inflation pressure on the
placard on the driver’s door B-pillar
( page 264). If necessary, add air to
achieve the recommended tire inflation
pressure.
i
If you have overfilled the tire, release
tire inflation pressure by pushing the
metal stem of the valve with e.g. a tip of
a pen. Then recheck the tire inflation
pressure with the tire gauge.
Install the valve cap.
Repeat this procedure for each tire.