ADB Active Even When DSC is Off

The DSC function ADB has been around for a long while on a wide variety of BMW vehicles and especially in the form of the ADB-X version on the xDrive models.

If one of the wheels of a driven axle is spinning, it cannot transmit any driving force (torque) to the road. And because the differential distributes the torque equally between the two wheels, the other wheel on the axle can not transmit any driving force either.

ADB brakes the spinning wheel so that the driving torque and braking force are in equilibrium on that wheel. Then, by virtue of the differential, an equal amount of driving torque is applied to the wheel that is not spinning. And because that wheel is offered grip by the road surface, a driving force can be transmitted that results in forward motion of the vehicle.

Thus ADB increases traction on slippery surfaces and has a similar effect to a differential lock.

• On the xDrive  models, ADB-X remains active even when the DSC is switch off in order to achieve improved traction, especially when driving off road.
• On vehicles with rear-wheel drive  , that individual braking of the driving wheels was previously only active when the DSC was active or in "DTC" mode.
• On the new F01/F02 (and the top 1 Series and 3 Series models) that ADB subfunction remains active even when the DSC is switched off.

That function is called "Electronic Differential Lock Control"  and uses the DSC to emulate the effect of a differential lock on the driving wheels. In contrast with previous arrangements, such brake modulation for the purposes of increasing drive transmission takes places even if the driver has switched off the DSC.