Mercedes-Benz 2008 M-Class Operator's Manual page 351

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 of less
1
than / in (3 mm).
8
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 approx-
1
imately / in (1.6 mm), at which point the
16
tire is considered worn and should be re-
placed.
Recommended minimum tire tread depth:
1
Summer tires / in (3 mm)
8
1
Winter tires / in (4 mm)
6
Warning!
Although the applicable federal motor safety
laws consider a tire to be worn when the
treadwear indicators (TWI) become visible at
1
approximately / in (1.6 mm), we recom-
16
mend that you do not allow your tires
350
to wear down to that level. As tread depth
1
approaches / in (3 mm), the adhesion
8
properties on a wet road are sharply
reduced.
Depending upon the weather and/or road
surface (conditions), the tire traction varies
widely.
G
1 TWI (Tread Wear 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.