Understanding the difference between xDrive and sDrive

BMW shoppers will most likely see badging that denotes either xDrive or sDrive on its range of vehicles. But what do these terms mean?

The terms xDrive and sDrive are BMWs nomenclature for which wheels the engine sends power to. Traditionally this was always to the rear wheels but with the rise in popularity of four wheel drive systems they had to come up with a way of differentiating between these two very different drivetrain systems. Basically sDrive means the car is two-wheel drive while xDrive signifies that power is sent to all four wheels.

sDrive

Many of the cars available in BMWs range are still two-wheel drive and will thus carry sDrive badging. While two wheel drive BMWs were traditionally rear-wheel drive, many models are now available in a front wheel drive configuration, such as the 1-Series.

Shoppers will also notice that some X models such as the X1 and X2 are also now available with sDrive. This gives those motorists that will never drive off-road or on slippery conditions the option of driving an SUV with its higher ground clearance but without any of the drawbacks of an all-wheel drive system, which could include a higher purchase price, increased fuel consumption and vehicle weight.

xDrive

xDrive is the brand name of BMWs all-wheel drive technology. Originally launched on SUV models like the X5 it is now available on models throughout BMWs range.

When driving normally xDrive sends around 40 percent of drive to the front wheels and 60 percent to the rear wheels. Depending on grip levels the systems sensors can shift power around to the wheels with the most grip in slippery situations like when driving off-road. The result is a vehicle with less possibility of unwanted traction loss in corners, when making sudden manoeuvres or in low grip environments.

xDrive uses an electronically controlled multi-disc clutch which is lightweight and can re-distribute power very quickly, in extreme conditions 100 percent of the power can be sent to either axle in 0.1 seconds, a process that is constantly monitored by the Dynamic Stability Control.

With cars getting more powerful with each model release, systems like xDrive go a long way in making cars safer, especially on less than ideal road surfaces that we have in South Africa as well as when driving on gravel roads or in a torrential downpour.

The advantages of xDrive include improved driving safety, as the system is active all the time but only steps in when necessary. xDrive constantly monitors the wheel speed of each wheel, steering angle and throttle position and distributes the power accordingly and this is what makes xDrive different to four-wheel drive.

Four-wheel drive systems distribute power evenly to the front and rear axle while with xDrive power is distributed to each wheel depending on the need. This allows traction to be optimised while power isn’t being wasted on wheels that don't require it.