25 Years of All-Wheel Drive BMWs

For 25 Years BMW has been a leader in all-wheel drive technology. From the first 325iX to the latest X3 all-wheel drive has been a important and continually growing part of BMW ‘s business. We at BF have often derided the need for all-wheel drive as being born out of marketing. And while it ‘s true that many people driving xDrive equipped cars may not need the system, there are those that not only need it but require it. It ‘s because of this that, 25 after it ‘s introduction, BMW has expanded the all-wheel drive option to almost every car they make. BMW currently offers 45 models in which xDrive provides variable distribution of drive between the front and rear wheels. These models extend all the way from the BMW X models via the BMW 3 Series and BMW 5 Series ranges to the BMW 7 Series family.

1985 saw all-wheel drive offered for the first time for the BMW 3 Series – both as an extension of the model range and as an alternative to the customary BMW rear-wheel drive. By now BMW was using the transfer of power to both axles not only to optimise traction on loose surfaces and in adverse weather conditions, but also to enhance dynamic performance though corners. The latest version of the BMW xDrive all-wheel-drive system rises to this challenge more effectively than ever. Linking the all-wheel-drive system up with Integrated Chassis Management (ICM) means that all situations on the road can be recognised and evaluated to allow the necessary control interventions to be made at an early stage. These can be carried out by xDrive either on its own or in combination with Dynamic Stability Control (DSC) or Performance Control. The power is distributed quickly and with great precision to where it is needed, ensuring that the driver enjoys the handling characteristics he would expect from a BMW – even under extremely dynamic cornering.

In contrast to other manufacturers, who use all-wheel drive principally to make up for the shortfall in traction suffered by front-wheel-drive vehicles, BMW tunes its xDrive system to provide handling typical of rear-wheel drive. Even in normal situations on the road, all-wheel-drive BMW models send the lion’s share of drive to the rear wheels, the same place where the brand’s cars with only one driven axle turn power into optimum dynamic performance. This ensures that the hallmark BMW steering precision is virtually free from drive forces in all-wheel-drive models as well. Indeed, all-wheel drive actually enhances the driving experience through corners. In order to enable particularly precise turn-in and a high level of directional stability, the latest-generation xDrive sends more drive to the rear axle on the way into corners. And that takes the brand’s characteristic driving pleasure to a new level once again.

All-wheel-drive technology from BMW: rigorous further development, dynamic growth.

Over the last 25 years at BMW, all-wheel drive has developed from an option initially limited to selected models to a growth driver for the ongoing expansion of the model range. At the time it was launched in the second-generation BMW 3 Series, all-wheel drive was offered exclusively in conjunction with a 2.5-litre six-cylinder in-line petrol engine producing 126 kW/171 hp. Today, xDrive can be specified for the BMW 3 Series in tandem with any of three six-cylinder petrol engines, a four-cylinder petrol unit and a six-cylinder diesel powerplant.

The permanent all-wheel drive of the BMW 325iX unveiled in 1985 channelled power to the front and rear wheels at a constant 37 : 63 percent split. Visco locks in the transfer case and final drive took their cues from the difference in rotation speed between the front and rear wheels to provide virtually fixed connections if required, and in this way optimise traction and driving stability. From 1988 customers could also order a Touring variant of the BMW 325iX.

Three years later came the arrival of all-wheel drive in the BMW 5 Series, accompanied by the debut of electric control systems governing the distribution of power. The newly developed system had multi-plate clutches which could be controlled automatically and continuously to vary the usual distribution of drive in normal conditions – 36 : 64 percent between the front and rear wheels – as required. Initially, a hydraulically controlled multi-plate clutch was used at the rear axle, but this was later replaced by electronically controlled brake inputs. The control unit of the all-wheel-drive system took into account wheel speed signals from the anti-lock braking system, the rotational speed and position of the engine’s throttle valves and the status of the brakes when analysing the driving situation.

From the outset the all-wheel-drive system of the BMW 525ix – fitted with a six-cylinder petrol engine developing 141 kW/192 hp – proved to be

a superior concept to that of its competitors. The electronic control system allowed extremely rapid and precise reactions, which also led to neutral and safe handling characteristics in tricky conditions on wet or snow-covered roads. The first all-wheel-drive BMW 5 Series was available in both Saloon and Touring guise.

The creation of the Sports Activity Vehicle (SAV) segment opened up totally new dimensions for all-wheel drive. BMW caused a sensation with the introduction of this innovative new vehicle concept in 1999. The BMW X5 captured the imagination of its customers with a level of dynamic performance unmatched among its off-road peers. The characteristics of the BMW all-wheel-drive system also served this set of priorities. In normal driving conditions, engine power was distributed at a ratio of 38 : 62 between the front and rear wheels via a planetary gear set, while the standard-fitted Dynamic Stability Control (DSC), Automatic Differential Brake (ADB-X) and Hill Descent Control (HDC) equipped the BMW X5 equally as well for sporty driving as for challenges off the beaten track.

X5

Innovative vehicle concepts and xDrive give BMW the edge.

Since the SAV concept successfully established itself in the shape of the BMW X5, BMW has been constantly building on its stand-out position in the all-wheel-drive vehicle market through the introduction of new models and the further development of its drive transfer system. All-wheel drive was made available for the BMW 3 Series once again as early as 2000 – this time in conjunction with two petrol engines and one diesel unit.

In 2004 BMW picked up the pioneering baton once more when it introduced the SAV concept into another vehicle segment. With more compact dimensions than the BMW X5 and even more agile handling, the BMW X3 was likewise very much one of a kind and indeed remained the only premium model in its class for a number of years.

BMW also stole a march on its competitors in the development of all-wheel-drive technology. The newly developed xDrive all-wheel-drive system, introduced for the BMW X5 alongside the launch of the BMW X3, boasted an extremely fast-working, electronically controlled multi-plate clutch in the transfer case and linked up with the DSC driving control system. This allowed it to provide an unrivalled platform for power distribution that could be adjusted as necessary at all times. For the first time, the driving situation could be analysed not only on the basis of wheel speed, but also using data supplied by the DSC system on steering angle, accelerator position and lateral acceleration, including the driving status deduced from these parameters. This laid the foundations for xDrive to become the world’s only intelligent all-wheel-drive system, a status it retains to this day. In contrast to conventional all-wheel-drive systems, which merely react to wheels that are already spinning, xDrive can identify any tendency to oversteer or understeer at an early stage and counteract it pre-emptively by adjusting the distribution of drive.

Over the years that followed it was not only the two X models that benefited from the exceptionally rapid and precisely calculated distribution of power, but also the BMW 5 Series Saloon and Touring models and the BMW 3 Series. In 2005, all-wheel-drive variants were introduced both for the fifth generation of the BMW 3 Series and for the fifth-generation BMW 5 Series launched a short time earlier. More than 600,000 units of the first-generation BMW X3 were sold worldwide before it handed over to the new model in 2010. A little earlier the BMW X5, the second generation of which had been in production since 2006, had passed the million-unit mark.

Assured traction, superior dynamics: BMW xDrive with new calibration and Dynamic Performance Control.

The extraordinary potential of both the BMW X model concept and xDrive technology has since spawned another wave of innovations. For example, the BMW X6 – still the world’s only Sports Activity Coupé – was launched in 2008, and the BMW ActiveHybrid X6 is also fitted with xDrive.

2010 BMW X1

Since 2009 the BMW X1 has been the only vehicle of its kind in the premium compact segment.

As in the new BMW X3, xDrive can also be combined with Performance Control in the BMW X1 to make its handling even more agile. Carefully calculated brake impulses applied to the inside rear wheel around a corner combine with a simultaneous increase in engine power to ensure that the vehicle turns in extremely quickly and precisely. The BMW X6 is fitted as standard with Dynamic Performance Control, giving it even greater scope for adjusting the distribution of power. This system teams up with xDrive to provide the most captivating expression yet of BMW’s hallmark driving pleasure through corners. Dynamic Performance Control uses variable distribution of drive between the inside and outside rear wheel to enable exceptional agility and stability around corners, even under sudden load changes or in overrun.

The interplay of xDrive and Dynamic Performance Control can be experienced at its most intense in the BMW X5 M and BMW X6 M. The first high-performance sports cars with all-wheel drive to come out of BMW M GmbH are powered by an eight-cylinder engine with M TwinPower Turbo technology developing 408 kW/555 hp.

Alongside the impressive progress of the BMW X models, the range of all-wheel-drive variants of other model series has also been consistently expanding. xDrive is now available not only for the Saloon and Touring versions of the BMW 3 Series but also for the Coupé; a total of 15 model variants from the 3 Series range now have all-wheel drive. Four engine variants of the BMW 5 Series Gran Turismo are also available with xDrive. With its new set-up designed to enhance agility and precision through corners, xDrive offers a better platform than ever when it comes to providing an intensive driving experience and an ideal combination of dynamic capability and comfort. It was therefore no surprise to see all-wheel drive also being welcomed into the BMW 7 Series range. Customers can choose from three all-wheel-drive variants of the luxury Saloon – the BMW 750i xDrive, BMW 750Li xDrive and BMW 740d xDrive.

In addition, xDrive intelligent all-wheel drive is set for launch in the new sixth generation of the BMW 5 Series Saloon. The system will be available initially in the BMW 550i xDrive powered by a 300 kW/407 hp eight-cylinder engine, with two six-cylinder models and the first xDrive variants of the new BMW 5 Series Touring following in due course.

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  • goat

    Good to see BMW returning Audi’s quattro nose-tweaking… but the return volley is still too oblique! If BMW wants their xDrive to be taken seriously as a dynamic driving system versus its current perception among enthusiasts as a “bad weather / safety system”, a couple of things need to happen – and quickly:

    (1) Offer sport suspension on xDrive cars (ZSP). In N.America at least it is a “hold your nose” type decision to spec xDrive on an e90, for example. Without ZSP, the car’s ride too soft and are visually unappealing with that much wheelwell gap. BMWPerformance does not offer an alternative. This leaves aftermarket… but taking delivery of a new BMW and needing to immediately swap suspension for coilovers or – worse – lowering springs to “sort” the handling and appearance is not appealing from perspective of added labour, compromised suspension warranty / dealer relationship, etc. Audi, conversely, offers sport suspension option on all their quattro sedans in both regular and S-line trim, then an even more performance-oriented suspension option in the very desirable S-level cars, to say nothing of the RS-level.

    (2) Active rear differential needs to be offered, similar to what Audi offers on the S-level cars. For BMW, this would give the xDrive variant a bona fide advantage over the RWD variants (particularly for non-M cars, since they – sadly – lack a rear LSD entirely!).

    BMW Canada has stated recently that, not only are nearly all dealer purchases currently of xDrive (over 95%?) but that they intend to increase this to very close to 100% xDrives sold in Canada. I can speak for myself and say that if this happens – without the simple suspension and drivetrain changes recommended above – many many BMW enthusiasts who come to BMW for the RWD handling dynamics will leave the brand for Audi. Reasoning? If we can’t have RWD handling dynamics in a sports sedan (with a sport suspension!), we may as well pick the AWD handling dynamics that are most sporting (currently offered by Audi, not BMW).

  • goat

    To clarify “active rear differential”, I mean the “torque vectoring” system in current S4 and available as an option in some Porsches, as well as at a (slightly) lower price point in Mitsu’s Evo. 🙂

  • (1) Offer sport suspension on xDrive cars (ZSP). In N.America at least it is a “hold your nose” type decision to spec xDrive on an e90, for example. Without ZSP, the car’s ride too soft and are visually unappealing with that much wheelwell gap.

    I personally love the fact that BMW has been historically against AWD in regards to performance. Brands don’t believe in anything anymore and it’s great to see BMW continuing to have a legacy in rwd performance vehicles.

    BMWPerformance does not offer an alternative.

    This is the only place I could personally be comfortable with BMW offering awd performance vehicles.

    Audi, conversely, offers sport suspension option on all their quattro sedans in both regular and S-line trim, then an even more performance-oriented suspension option in the very desirable S-level cars, to say nothing of the RS-level.

    VW made the marketing decision long ago to differentiate Audi by using AWD. They had to considering how closely related Audis were to their cheaper VW cousins.

  • Evan

    I’ll second the need for a sport suspension option on AWD 3er models. I would still buy a RWD 3er livinig in New England in order to get a sports suspension. In the end, I’m still not convinced that AWD is needed- there are so few days that you really need it out of a year- that the added weight, complexity, and thusly fuel mileage hit aren’t quite worth it. Perhaps if I lived on a dirt road that wasn’t paved in the winter, then I’d need it. But just being in a “snowy” region isn’t enough.

  • JonPD

    Sorry to say but I would label this article as 25 years of the death of fun. Give me a FWD or RWD and I can navigate 99% of what a AWD vehicle can. Also the base fact that when it comes to bad weather drivers of AWD and 4×4 vehicles are some of the first to miss to call in due to weather in my experience. BMW AWD is interesting but it just broadly changes the feel behind the wheel. AWD has been sold as a safety device, meanwhile I cannot begin the numbers of crashed AWD and 4×4 vehicles that think their safe vehicle is invincible.

  • chas58

    I did an AWD gravel hill climb like in that first B&W photo. That is the only time I really needed AWD though (and not what I typically do in a BMW).

    So, I went back to RWD as it is simpler, better handling, better milage, cheaper purchase, less maintenance.

    Yeah, if I lived in snowy mountains I would have a stronger argument for AWD. However it really is an excuse for people not to use snow tires. I kinda understand, but last winter I was almost rear ended by a 328xi who lost control & spun when they tried to brake behind me – AWD didn’t help with that.

  • BMW offered torque vectoring BEFORE Audi, it was introduced exclusively on the X6 at launch- later to be featured on the X M vehicles. It is marketed as dynamic performance control. Worth noting is that the latest xDrive uses new algorithms to brake the inside wheel providing effectively 95% of the diff system. The new xDrive was launched in the new 7.

    Sport suspension is not an option as the motor, oil pan et al. Are designed to have the shafts for the FWD run through them. Audi puts the engine in front of this though some new models have made this less prevelent.

    -M

  • goat

    @Gabe – you may have misunderstood my intent… Like you, I see BMW as the last ambassador for RWD sport sedans (just ordered a 335i e90 stick shift sport package in RWD, not xDrive, for the driving dynamics and feel this driveteain configuration alone yields… and yes up here in Canada no less!). 🙂

    But I do feel that BMW is saying one thing (trading on image of pure RWD sporting-chassis cars) and doing another (selling xDrive models nearly exclusively, sport suspension not available from them even as BMWPerformance items). You want a BMW in RWD? Quite likely need to special order it. You also want to shift your gears manually? You DEFINITELY need to special order. That delta between marketing and what is being sold in ever-increasing numbers is what I mean to emphasize. It’s a point i know you and the gang on bimmercast have made before as well. Is BMW listening or are we destined to an AWD future – but sans sport suspension tuning support by BMW? I like to think there will be a renaissance of RWD but I may be wishing too sunnily. 🙂

    @Michael – glad to hear BMW torque vectoring is moving from the SAV’s to the sedans. Expect it will trickle down from the new 7 to the 3 even in next generation, which is good. As for not being able to offer sport suspension on xDrives, many owners have fitted coilovers at greater drops than the 10-15mm ride height difference between RWD ZSP and xDrives, just too bad we can’t see an OEM-engineered solution to this yet!

  • goat

    @jonPD – agree about many AWD drivers feeling invincible enough to run “performance all seasons” year-round yet often showing more difficulty negotiating snowy conditions than a 2300lb RWD Miata with truly minimal ground clearance… good weight distribution, SNOW TIRES, the control afforded by a manual gearbox, and common sense and respect for the laws of physics are wonderful allies in poor weather too. (Up here Quebec has done this right – snow tires are mandated by law from mid-November until spring.)

  • JonPD

    Over the years I have successfully navigated every imaginable road condition successfully in a RWD or FWD vehicle. This included multiple trips in the dead of winter over some of the nastiest passes in the nation. A little common sense and proper tires win over AWD most every time driven by ignorant drivers that believe marketing hype without using any common sense to modify their driving habits or to get proper tires on their cars.

    Still remember driving my GP up to go skiing in a heavy snowstorm. On the way stopped to check on a car that went off the road. There set a pretty space gray 335i X Drive with a set of Potenza RE-11 tires crumpled in a ditch. I have seen this more times than I can count over the years.

    To add to this the extra weight and drastic change in handling I declare it not much more than a warm blanket trying to convince people they are safe. Thanks but personally I will leave the nanny state far behind every time.

  • goat

    @JonPD: good story and +1!

  • PC in Ohio

    Great article, Gabe. I enjoy listening to you and Michael on my iPhone as well and have learned a lot. I live in the “snowbelt” of Northeast Ohio averaging ~ 100 inches of snow per year. I’ve always driven FWD with snow tires but am planning on getting a BMW 3 series soon and am leaning toward the AWD because of my geographic situation. RWD with snows is the better enthusiast choice though, but just not sure if it’s right for me.