The xDrive system in M cars is like everything else on an M machine, geared towards performance and built to retain the traditional character of an M car. M xDrive is obviously biased towards the rear, preserving the RWD-esque behavior that drivers expect from a car with an M badge while also providing the advantages of an AWD system.
These models have no default torque split, as the power is constantly shifted to provide the most grip. You can adapt the system via the drive modes, however. In 4WD Sport, the system will allow some slip on the rear wheels before sending power to the front. Basically, it will let you hang the tail out for a bit before intervening.
The latest M cars also come with a 2WD mode, which allows the driver to completely disengage the front axle, sending 100% of the power to the rear. In this mode, which is usually used for hooning, the front axle will not engage under any circumstances, which is why BMW recommends only using it on the track.
The M xDrive system is available on the following models:
