Mercedes-Benz SLR McLaren. Operator's Manual.

Operation
Tires and wheels
Tread depth
Do not allow your tires to wear down too
far. Adhesion properties on wet roads are
sharply reduced at tread depths under
1
/8 in (3 mm).
Treadwear indicators (TWI) are required by
law. These indicators are located in six
places on the tread circumference and
become visible at a tread depth of approximately
1 / 16 in (1.6 mm), at which point
the tire is considered worn and should be
replaced.
Recommended minimum tire tread depth:
Summer tires 1 / 8 in (3 mm)
Winter tires 1 / 6 in (4 mm)
Warning! G
Although the applicable federal motor safety
laws consider a tire to be worn when the
treadwear indicators (TWI) become visible at
approximately 1 / 16 in (1.6 mm), we recommend
that you do not allow your tires
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to wear down to that level. As tread depth
approaches 1 / 8 in (3 mm), the adhesion
properties on a wet road are sharply
reduced.
Depending upon the weather and/or road
surface (conditions), the tire traction varies
widely.
1 TWI (TreadWear Indicator)
The treadwear indicator appears as a solid
band across the tread.
Storing tires
!
Keep unmounted tires in a cool, dry
place with as little exposure to light as
possible. Protect tires from contact
with oil, grease and gasoline.
Cleaning tires
!
Never use a round nozzle to power
wash tires. The intense jet of water can
result in damage to the tire.
Always replace a damaged tire.
Warning! G
Have worn or damaged tires replaced in
pairs (front pair or rear pair) an make sure
the tires rotate in the direction specified
( page 257). Otherwise, the driving stability
of the vehicle will be adversely affected,
especially when driving at high speeds.