Most BMW since 1994 came with some form of "traction control" system - either ASC+T or DSC. When wheels slip or a loss of traction is detected, the traction control system automatically reduces engine RPM's and applies the anti-lock brakes if traction isn't restored quickly. The system does this much faster than a driver can usually react. While this is great for reducing or avoiding skidding and sliding in snow, ice, or on sandy shoulders, it can make it virtually impossible to get to the top of a slippery hill. Here's what happens: the rear wheels begin to spin. engine throttle is reduced, the anti-lock braking system kicks in and your BMW slows to a stop part-way up the incline. This happens even if you give yourself a running start.
You can disable the traction control by pushing the button on your console (labeled ASC
pr DSC). When you do, the traction conttrol light will illuminate on the dash. But disabling the traction control doesn't always help. On a slippery hill with no ABS in play and full power going to the rear wheels, they will spin like mad. In a few conditions (e.g. fluffy snow), the fast spinning will allow the tires to burrow down to a surface where they can get enough traction to inch the car forward.... MAYBE. But on most slippery roads, all this does is cause the rear end or your BMW to slide sideways towards even bigger trouble. Woundn't be great if you could use the non-slip aspect of the ABS system without the reduction in power? Well.... you can. Heres how:
Push and hold the ASC or DSC button; the traction control light will illuminate for several seconds (about 10), then go off. Once the light is off, release the button. Your BMW's traction control system is now in a mode where ABS will be applied to wheels that lose traction, but the engine throttle will not be reduced!!
NOTE: Unlike normal traction control operation, where you can go from ON to OFF and back again just by pushing a button, once your BMW is in this "half mode", the only way to deactivate it is to turn the engine off. The next time you start the enigne, it will revert to normal mode (traction control ON).
I saw this in "Fast Times" the newsletter of Bavarian Autosport. Looking forward to trying it out this winter, Rob