Snow Chain Switch

Snow Chain Switch:

In deep snow with tire chains installed, the sensitive, stability-oriented ASR system can have an adverse effect on standing starts. Therefore the system program includes a special control logic which the driver can select with the ASR snow chain switch. When the driver pushes the snow chain switch, the LED indicator in the switch comes on. After a 50 ms delay, the system allows more drive spin at the wheels, so in the situations mentioned above the driver can work the vehicle free. Because the increased spin would have a negative effect on handling (particularly at higher speeds), it is limited to speeds below 40 km/h (25 mph). The increased spin program is stored in the control unit up to a speed of 60 km/h (37 mph) and will be activated again if the speed drops below 40 km/h (25 mph). If the vehicle speed exceeds 60 km/h (37 mph) the increased spin program is erased from the memory and the LED indicator in the switch goes out. The snow chain logic program can also be manually canceled by toggling the switch off. The snow chain switch need not be used with snow tires.

NOTE: The driver should activate this switch when driving in deep snow with snow chains installed.

After the switch is engaged, an LED indicator comes on, confirming selection of a raised spin threshold by the ABS/ASR control unit.

Activation: Push above - ON
Push below - OFF

Spin Thresholds:

The spin threshold is raised at lower vehicle speeds (under 40 km/h, 25 mph) after the first 50 ms of normal ASR control operation. Between driving speeds of 40 to 60 km/h (25 to 37 mph) the memory retains the raised spin threshold. If the vehicle speed exceeds 60 km/h (37 mph), the memory of the raised spin threshold is erased.

Because of the raised spin threshold, the wheel speed differences between the front and rear wheels can be greater. This way a stuck vehicle can be worked loose. In deep snow with snow chains installed, this achieves the most traction possible. For vehicle handling, this raised threshold operation stops above 40 km/h (25 mph).