BMW xDrive is the marketing name for the
all-wheel drive
An all-wheel drive vehicle (AWD vehicle) is one with a powertrain capable of providing power to all its wheels, whether full-time or on-demand.
The most common forms of all-wheel drive are:
;1x1 : All unicycles Reflecting one axle with one w ...
system found on various BMW models since 2003. The system uses an electronically-actuated clutch-pack differential to vary the torque between the front and rear axles. Models with the DPC torque vectoring system also have a planetary gearset to overdrive an axle or rear wheel as required.
Prior to the introduction of xDrive, all-wheel drive was available on several models since 1985, based on an all-wheel drive system that uses viscous couplings.
Predecessor
The first BMWs available with all-wheel drive were the 1985-1992
E30 325iX and 1991-1996
E34 525iX models. These cars use centre and rear differentials with
viscous couplings to vary the torque split between wheels. The centre differential has a default front:rear torque split of 37:63, due to the planetary gear. Up to 80% of the torque can be transferred to the tripping axle, using the increasing shear force of the silicone fluid in the viscous coupling (due to the slotted/grooved plates inside the unit) as wheel slip causes one axle to spin faster than the other. The same principle applies to the rear differential varying the torque split between the rear wheels. The front differential has no locking function. All-wheel drive was discontinued when the E30 3 Series and E34 5 Series were replaced by the E36 and E39 respectively.
All-wheel drive was reintroduced in 2001 for the
X5 SUV and
E46 3 series 325xi, 330xi and 330xd sedans/wagons. The system is similar to the earlier version, except without the viscous couplings. Instead, the
electronic stability control
Electronic stability control (ESC), also referred to as electronic stability program (ESP) or dynamic stability control (DSC), is a computerized technology that improves a vehicle's stability by detecting and reducing loss of traction ( skiddi ...
(DSC) system applies the brake to wheels that are slipping, helping transfer power to the wheels with traction.
Design
Unlike its predecessor, the xDrive system uses an electronically-actuated
clutch-pack differential that engages to send torque to the front axle. In the case of the 2018 X3 through X6 models, the default torque split is 40:60 and the system is able to send 100% of the torque to either axle. However, full torque transfer to the front axle can only be achieved if the rear wheels have absolutely no traction, as the rear drive shaft is hard-coupled to the transmission output,. The wet clutch is applied through a high speed electric
servo motor
A servomotor (or servo motor) is a rotary actuator or linear actuator that allows for precise control of angular or linear position, velocity and acceleration. It consists of a suitable motor coupled to a sensor for position feedback. It also r ...
turning a cam-shaped actuator disc. In most vehicles, the system uses open differentials at the front and rear, relying on the brakes (controlled by the electronic stability control system) to transfer torque away from the slipping wheel on each axle.
A different system is used on BMWs which are based on a
transverse engine
A transverse engine is an engine mounted in a vehicle so that the engine's crankshaft axis is perpendicular to the direction of travel. Many modern front-wheel drive vehicles use this engine mounting configuration. Most rear-wheel drive vehicles ...
front-wheel drive platform, such as the
BMW X1 (F48)
The F48 BMW X1 is the second generation of the BMW X1 range of subcompact luxury crossover SUV. The F48 X1 was unveiled at the September 2015 Frankfurt Motor Show, and later at the 2015 Tokyo Motor Show. Contrary to the previous generation whic ...
,
BMW 1 Series (F40)
The BMW 1 Series (F40) is the third generation of the BMW 1 Series range of subcompact executive hatchback cars. Unlike the previous generation F20 1 Series, the F40 1 Series uses a front-wheel drive configuration and is only available as a 5-d ...
and
BMW 2 Series Active Tourer
The BMW 2 Series Active Tourer (F45/U06 model code) is a two-row subcompact executive MPV produced by BMW since August 2014. The closely related BMW 2 Series Gran Tourer (F46 model code) is a longer three-row version which began production in ...
. These models use a
Haldex system which sends 100% of the torque to the front wheels by default, only sending torque to the rear wheels when the front wheels are slipping.
Dynamic Performance Control
An upgraded version of xDrive with
torque vectoring
Torque vectoring is a technology employed in automobile differentials that has the ability to vary the torque to each half-shaft with an electronic system; or in rail vehicles which achieve the same using individually motored wheels. This method ...
, called 'Dynamic Performance Control' (DPC), was introduced on the 2008
BMW X6
The BMW X6 is a mid-size luxury crossover SUV by German automaker BMW. The BMW X6 is the originator of the sports activity coupé (SAC), referencing its sloping rear roof design. It combines the attributes of an SUV (high ground clearance, all- ...
and has since become available on other vehicles including the
BMW X5 M. As per most torque vectoring systems, the primary function is to increase agility in cornering.
The DPC system is also used by the
electronic stability control
Electronic stability control (ESC), also referred to as electronic stability program (ESP) or dynamic stability control (DSC), is a computerized technology that improves a vehicle's stability by detecting and reducing loss of traction ( skiddi ...
(DSC) to correct for understeer/oversteer, with one reviewer commenting that it provided smoother results and avoided the temporary power loss associated with the traditional method of using individual wheel brakes in such situations.
The DPC system can distribute torque between the front and rear axles, and between the two wheels on the rear axle. The system uses a clutch pack and
planetary gearset
An epicyclic gear train (also known as a planetary gearset) consists of two gears mounted so that the center of one gear revolves around the center of the other. A carrier connects the centers of the two gears and rotates the planet and sun gea ...
within the differential to overdrive a wheel or axle as required.
Applications
The first models xDrive models (as opposed to the earlier all-wheel drive system) were released in 2003. These consisted of the newly released
BMW X3 (E83)
The BMW X3 is a compact luxury crossover SUV manufactured by BMW since 2003, based on the BMW 3 Series platform. Now in its third generation, BMW markets the car as a ''Sports Activity Vehicle'', the company's proprietary descriptor for its X- ...
, facelifted
BMW X5 (E53)
The BMW E53 is the first generation BMW X5 mid-size luxury crossover SUV. The vehicle was the first SUV ever produced by BMW. It was produced between 1999 and 2006 and was replaced by the E70 X5.
The E53 X5 was developed just after the acqui ...
. In the following years, the availability of xDrive increased throughout the model range, and it is currently available on most models.
The first
BMW M
BMW M GmbH, formerly known as BMW Motorsport GmbH, is a subsidiary of BMW, BMW AG that manufactures high-performance cars.
BMW M ("M" for "motorsport") was initially created to facilitate BMW's racing program, which was very successful in the ...
models to use xDrive were the 2009
E70 X5M and
E71 X6M models. The first non-SUV BMW M model to not be rear-wheel drive was the 2017
F90 M5, which was only available with xDrive.
In Canada, 50 percent of BMWs sold in 2005 were fitted with xDrive. As of 2010, BMW Canada stopped offering rear-wheel drive versions of models that were available with xDrive, for example the only
BMW 6 Series (F12) 650i version available without xDrive in 2012 was the convertible version.
References
{{BMW
BMW
Four-wheel-drive system tradenames