2008 Mercedes R-Class Owner's Manual - Page 366

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 than 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 /6 in (4 mm) Warning! 1 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. 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 fuels. 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. Direction of rotation Unidirectional tires offer added advantages, such as better hydroplaning performance. To benefit, however, you must make sure the tires rotate in the direction specified. An arrow on the sidewall indicates the intended direction of rotation (spinning) of the tire. G 1 TWI (Tread Wear Indicator) The treadwear indicator appears as a solid band across the tread. 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 to 365