BMW M xDrive explained: how the all-wheel drive of M cars works

BMW M xDrive is the all-wheel-drive system that BMW M introduced with the M5 F90 in 2017. For decades, M cars were proudly rear-wheel drive only, so many fans were worried. But M xDrive was designed to feel like a rear-wheel-drive car, and it can even switch the front axle off completely.

In this article we explain how BMW M xDrive works, what the 4WD, 4WD Sport and 2WD modes do, the role of the Active M Differential and when each setting makes sense.

Why BMW M switched to all-wheel drive

For more than thirty years, the M5 and the M3 sent their power only to the rear wheels. That was part of their character: a balanced chassis, a clear feeling at the limit and the possibility to steer the car with the throttle.

But power kept rising. When the F10 M5 reached 560 hp and more, traction became a real limit, especially in wet or cold conditions. A large part of the power simply could not reach the road when accelerating out of slow corners or from a standstill.

All-wheel drive solves this problem. With four driven wheels, a car can use much more of its power, more of the time. The challenge for BMW M was to add this traction without making the cars feel heavy, nose-heavy or numb, which is a common criticism of all-wheel-drive performance cars.

The answer was M xDrive: an all-wheel-drive system tuned to be strongly rear-biased, combined with an electronically controlled rear differential and the possibility to drive in pure rear-wheel-drive mode.

How BMW M xDrive works

M xDrive is based on BMW's xDrive system, but with its own hardware and software. At the heart of the system is a transfer case with an electronically controlled multi-plate clutch. It sits behind the gearbox and decides how much torque goes to the front axle.

In normal driving, most of the power goes to the rear wheels. Only when the system detects that the rear wheels are about to lose traction, or when the driving situation needs it, does the clutch close and send more torque forward. The adjustment happens in a fraction of a second and continuously.

At the rear, the Active M Differential distributes the torque between the left and right wheels. It can lock up to 100 per cent, which helps the car turn into corners and accelerate out of them with maximum traction.

The control units of the engine, gearbox, transfer case, differential and the DSC stability control all work together. They use data from wheel speed sensors, steering angle, yaw rate and throttle position to decide the best distribution at every moment.

The three modes: 4WD, 4WD Sport and 2WD

M xDrive offers different settings, selected in the M setup menu or with the M buttons on the steering wheel.

• 4WD is the standard mode. It gives maximum traction and stability, and it is the right choice for everyday driving and bad weather. The car still feels rear-biased, but the front axle helps whenever needed.
• 4WD Sport sends more torque to the rear and allows more slip at the rear wheels before the front axle intervenes. The car feels more playful and agile, which suits a dry road or a track.
• 2WD disconnects the front axle and turns the car into a pure rear-wheel-drive M car. It is only available with DSC switched off, and it is meant for experienced drivers on a closed track.

The modes can also be combined with the DSC settings: DSC on, M Dynamic Mode (MDM) with more freedom, and DSC off. This gives the driver a wide range of characters, from very safe to completely unfiltered.

How it feels on the road

The biggest surprise for many drivers is how natural M xDrive feels. In normal driving, you hardly notice that the front wheels are driven. The steering stays light and precise, without the tugging that some all-wheel-drive cars have under acceleration.

The real difference appears when you accelerate hard. Where a rear-wheel-drive M car with this much power would struggle for grip, the M xDrive car simply goes. Out of a slow corner, or from a standstill in the wet, the car puts its power down with very little drama.

In 4WD Sport, the rear axle does more of the work and the car rotates more willingly through corners. Experienced drivers can feel the rear move slightly before the front axle pulls the car straight.

For most people on public roads, 4WD is the best setting. It makes the car faster and safer in real conditions, which is exactly why BMW M chose this system.

Which BMW M cars use M xDrive

M xDrive started with the M5 F90 in 2017, including the M5 Competition and the M5 CS. It was then used in the M8 coupé, convertible and Gran Coupé, and in the M models of the X range, such as the X5 M and X6 M.

The current M3 and M4 (G80 and G82) are available with rear-wheel drive or with M xDrive, depending on the version and the market. The M3 Touring was launched with M xDrive as standard. The latest M5 G90 and the M5 Touring G99 also use M xDrive, combined with a hybrid drive.

Rear-wheel drive remains available on some models, such as the M2, and on rear-wheel-drive versions of the M3 and M4. So buyers can still choose the classic layout if they prefer it.

For many owners, the possibility to switch between all-wheel drive and rear-wheel drive offers the best of both worlds: traction when it is needed, and the classic M feeling when they want it.

Maintenance and things to know

M xDrive adds components that need care. The transfer case and the front differential have their own oil, and the Active M Differential at the rear needs regular attention as well. Follow the service schedule, and consider more frequent fluid changes if the car is used on track.

Tyres are very important. All four tyres should be the same brand, model and condition, with the correct sizes front and rear. Large differences in wear between the front and rear tyres can stress the transfer case, because the system has to compensate for the different rolling circumferences.

When towing a car with M xDrive, follow the instructions in the owner's handbook. In most cases, the car should be transported on a flatbed and not towed with two wheels on the ground.

Finally, remember that 2WD mode with DSC off removes most electronic help. It is a mode for the track, with experience and space, not for public roads.

M xDrive at a glance

Item	Details
Introduced	2017 with the BMW M5 F90
Layout	Rear-biased all-wheel drive
Front axle drive	Electronically controlled multi-plate clutch in the transfer case
Rear differential	Active M Differential, up to 100% locking
Modes	4WD, 4WD Sport, 2WD (2WD only with DSC off)
Used in	M5 F90/G90, M8, M3/M4 xDrive, X5 M, X6 M and more
Maintenance	Transfer case and differential oil, matching tyres

Frequently asked questions

What is BMW M xDrive?

M xDrive is the all-wheel-drive system of BMW M cars. It is rear-biased, uses an electronically controlled clutch to send torque to the front axle and works with the Active M Differential at the rear.

Can BMW M xDrive be switched to rear-wheel drive?

Yes. On models such as the M5, M3 and M4 with M xDrive, a 2WD mode disconnects the front axle. It is only available with DSC switched off and is meant for the track.

What is the difference between 4WD and 4WD Sport?

4WD gives maximum traction and stability. 4WD Sport sends more torque to the rear and allows more rear wheel slip, which makes the car feel more agile and playful.

Which was the first BMW M car with all-wheel drive?

The BMW M5 F90, launched in 2017, was the first M5 and the first core M model with M xDrive all-wheel drive.

Does M xDrive need special maintenance?

Yes. The transfer case and the differentials need regular oil service, and the four tyres should match in brand, model and wear to protect the system.

Sources

• BMW Group PressClub – press material on M xDrive and the BMW M5 (F90)
• BMW M – technology of BMW M cars
• BMW M5 (F90) owner's handbook – drive modes and DSC