BMW xDrive
Encyclopedia
BMW xDrive is BMW
's four-wheel drive
system that powers the X1
, X3
, X5
, X6
and 2006 and later xd and xi 3 Series
, 5 Series
and 7 Series
models. BMW confirmed it has plans for an xDrive M5.
Before xDrive, BMW offered 4WD as an option in the 1980s for the 3 series and the 5 series. The system had a planetary center differential with a permanent 38-62 (front-back) torque split. Both the center and rear differential had a viscous lock
which would engage automatically if slippage occurred (one shaft rotated at a significantly different speed compared to the other). The front differential had no lock of any kind.
4WD was again offered for the X5 and the 2001 3 series. The system was similar to the earlier system except without any of the locks. Instead, slipping wheels would be braked with the DSC system
, helping transfer power to the wheels with traction.
xDrive was introduced in 2003 with the new X3. Instead of a permanent torque split (which the earlier systems exhibit), xDrive provides torque split between the front and rear axles through the use of a multi-plate wet clutch
located in the gearbox on the output to the front drive shaft. This setup allows xDrive to modulate the torque split between the front and the rear. If wheel slip was detected by the ABS/DSC system, xDrive will react quickly to adjust torque bias. The wet clutch is applied through a high speed electric servo motor
turning a cam shaped actuator disc.
xDrive is connected to the ABS and DSC systems. In the case that wheelspin or directional instability still occurs while xDrive is or has been modulating the torque split, DSC will brake independent wheels to regain traction and improve directional stability without driver intervention.
The front and rear differentials in xDrive vehicles are an open differential design, thus relying on brake application by the DSC system to transfer power from the slipping wheel to the wheel with traction.
BMW
Bayerische Motoren Werke AG is a German automobile, motorcycle and engine manufacturing company founded in 1916. It also owns and produces the Mini marque, and is the parent company of Rolls-Royce Motor Cars. BMW produces motorcycles under BMW Motorrad and Husqvarna brands...
's four-wheel drive
Four-wheel drive
Four-wheel drive, 4WD, or 4×4 is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously...
system that powers the X1
BMW X1
The BMW X1 is a compact luxury crossover manufactured by BMW. It extends the current BMW Sports Activity Series model lineup which includes the BMW X3, BMW X5, and the BMW X6. The X1 is based on the same platform as the BMW 3 Series Touring with xDrive...
, X3
BMW X3
The BMW X3 is a compact crossover SUV marketed by the German automaker BMW, based on the BMW 3-Series automobile platform, and now in its second generation. BMW designed the X3 in conjunction with Magna Steyr of Graz, Austria — who manufactured all X3s under contract to BMW for the first...
, X5
BMW X5
The BMW X5 is a luxury crossover SUV introduced in 1999 as the first generation E53. It was BMW's first SUV also known as "Four-by-Four" in the UK. It features all-wheel drive which is branded as the "X" drive system and is available with either manual or automatic transmission...
, X6
BMW X6
The BMW X6 is a mid-size luxury crossover released for sale in the second quarter of 2008 by German automaker BMW. The X6 was marketed as a Sports Activity Coupé by BMW...
and 2006 and later xd and xi 3 Series
BMW 3 Series
The BMW 3 Series is a compact executive car manufactured by the German automaker BMW since May 1975. Successor to the BMW New Class, it has been produced in five different generations and in no less than five different body styles. It is BMW's best-selling model, accounting for around 30% of the...
, 5 Series
BMW 5 Series
The BMW 5 Series is a mid-size / executive car manufactured by BMW since 1972. The car, now in its sixth generation, is sold in sedan and touring body styles....
and 7 Series
BMW 7 Series
The BMW 7 Series is a line of full-size luxury vehicles produced by the German automaker BMW. Introduced in 1977, it is BMW's flagship car and is only available as a sedan or extended-length limousine...
models. BMW confirmed it has plans for an xDrive M5.
Before xDrive, BMW offered 4WD as an option in the 1980s for the 3 series and the 5 series. The system had a planetary center differential with a permanent 38-62 (front-back) torque split. Both the center and rear differential had a viscous lock
Viscous coupling unit
A viscous coupling is a mechanical device which transfers torque and rotation by the medium of a viscous fluid. It is made of a number of circular plates with tabs or perforations, fitted very close to each other in a sealed drum. Alternate plates are connected to a driving shaft at one end of the...
which would engage automatically if slippage occurred (one shaft rotated at a significantly different speed compared to the other). The front differential had no lock of any kind.
4WD was again offered for the X5 and the 2001 3 series. The system was similar to the earlier system except without any of the locks. Instead, slipping wheels would be braked with the DSC system
Electronic stability control
Electronic stability control is a computerized technology that may potentially improve the safety of a vehicle's stability by detecting and minimizing skids. When ESC detects loss of steering control, it automatically applies the brakes to help "steer" the vehicle where the driver intends to go...
, helping transfer power to the wheels with traction.
xDrive was introduced in 2003 with the new X3. Instead of a permanent torque split (which the earlier systems exhibit), xDrive provides torque split between the front and rear axles through the use of a multi-plate wet clutch
Clutch
A clutch is a mechanical device which provides for the transmission of power from one component to another...
located in the gearbox on the output to the front drive shaft. This setup allows xDrive to modulate the torque split between the front and the rear. If wheel slip was detected by the ABS/DSC system, xDrive will react quickly to adjust torque bias. The wet clutch is applied through a high speed electric servo motor
Servo motor
thumb|right|200px|Industrial servomotorThe grey/green cylinder is the [[Brush |brush-type]] [[DC motor]]. The black section at the bottom contains the [[Epicyclic gearing|planetary]] [[Reduction drive|reduction gear]], and the black object on top of the motor is the optical [[rotary encoder]] for...
turning a cam shaped actuator disc.
xDrive is connected to the ABS and DSC systems. In the case that wheelspin or directional instability still occurs while xDrive is or has been modulating the torque split, DSC will brake independent wheels to regain traction and improve directional stability without driver intervention.
The front and rear differentials in xDrive vehicles are an open differential design, thus relying on brake application by the DSC system to transfer power from the slipping wheel to the wheel with traction.