See also:

Treadwear indicators
Narrow bars (tread wear bars) that are distributed over the tire tread. If the tire tread is level with the bars, the wear limit of 1/16 in (1.6 mm) has been reached. ...

Servicing the brakes
If the red brake warning lamp lights up in the instrument cluster and you hear a warning tone while the engine is running, the brake fluid level may be too low. Observe additional warning messa ...

Tips for driving with DISTRONIC
The following contains descriptions of certain road and traffic conditions in which you must be particularly attentive. In such situations, brake if necessary. DISTRONIC is then deactivated. WARN ...