BMW’s xDrive system drives all the wheels, splitting the power 40:60 between front and rear, maintaining the rear drive bias for more enjoyable handling, but giving better grip in corners whenever conditions deteriorate, such as in rain or muddy conditions. It’s a simple idea, but to get the best from it, power needs to be able to vary between front and back axles, and between the left and right sides of the car.

An electronically-controlled gearbox and multi-plate clutch system allows BMW 4x4 models fitted with xDrive to vary the power between the front and back axles. If snow makes a wheel slip, xDrive reacts in a tenth of a second to redistribute power to the axle with the most grip.


Dynamic Stability Control.

Dynamic Stability Control (DSC) is the technology that BMW models with xDrive use to stop wheels spinning once they lose grip. For example, in the BMW X1, if mud causes a wheel to spin it’s detected in a fraction of a second and the brakes applied to it to limit spinning.

The system is also triggered by understeer or oversteer, even before wheels start to spin – if sensors detect that the car is not going where the driver is steering, individual wheels are braked to allow the driver to regain control. This happens in a fraction of a second, and often without the driver being aware that the system has intervened.

It’s important to note that DSC doesn’t give better cornering, but is instead a safety mechanism, helping the driver to regain control in tricky situations.


Dynamic Performance Control.

Some BMW 4x4 models, such as the BMW X6, are also fitted with Dynamic Performance Control. Working in combination with DSC, it uses a series of electronically controlled clutch plates to speed up the slower moving wheel.

This is known as torque vectoring and gives smoother turns; for example, on a bend more power is given to the outer wheel, because that wheel will have a grip advantage. Or if understeer is detected, more power will be directed to the inner wheel, so that traction with the road is regained.


Hill Descent Control.

When faced with descending a hill off-road there’s the option of engaging Hill Descent Control. This regulates the speed, keeping it at little more than walking pace, without the need to touch the brakes. The descent speed can be adjusted via the iDrive controller and should you need to touch the brakes on the way down, the system distributes the force according to the traction on each wheel. 

When it’s switched off at the bottom of the hill, it gradually reduces the braking force, giving the driver enough time to take control of the vehicle’s speed. The control display will also show front/back and side-to-side tilt in degrees or percent, as well as a graphic representation of the steering angle.