2008 Mercedes R-Class Owner's Manual - Page 345

Operation Driving instructions 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. The treadwear indicator appears as a solid band across the tread. Warning! Specified tire inflation pressures must be maintained. This applies particularly if the tires are subjected to high loads (e.g. high speeds, heavy loads, high ambient temperatures). Warning! Tire traction The safe speed on a wet, snow covered or icy road is always lower than on a dry road. You should pay particular attention to the condition of the road whenever the outside temperatures are close to the freezing point. Warning! G G Although the applicable federal motor vehicle 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 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. Do not drive with a flat tire. A flat tire affects the ability to steer or brake the vehicle. You may lose control of the vehicle. Continued driving with a flat tire or driving at high speed with a flat tire will cause excessive heat build-up and possibly a fire. G If ice has formed on the road, tire traction will be substantially reduced. Under such weather conditions, drive, steer and brake with extreme caution. For more information, see "Tires and wheels" ( page 363). Hydroplaning Depending on the depth of the water layer on the road, hydroplaning may occur, even at low speeds and with new tires. Reduce vehicle speed, avoid track grooves in the road and apply brakes cautiously in the rain. 344