Automotive Engineer

Since BMW introduced the 5 Series estate in 1991, the OEM has tried to balance the need for it to have the driveability of a sedan with the practicality of greater luggage space. 

It’s a blend that customers like. BMW has sold more than 650,000 since the vehicle’s inception. But the market is becoming increasingly competitive. The Audi A6 and Mercedes-Benz E-Class estates are the obvious alternatives, but even vehicles like the Audi A7 Sportback and BMW’s own 5 Series GT compete in the market now.

The fourth-generation 5 Series estate is destined for not only Europe and North America, but also the growing Asian market, where comfort is highly prized.

Arno Keller, 5 Series Touring project leader, says: “If you look at our products, we have increased our Asian market share, so they’re not only European or American vehicles any more. And if you want to have success in Asia you need to offer even more comfort.”

Because of that, Keller and his team have moved away from the third-generation vehicle’s chassis design. A double wishbone suspension replaces a MacPherson strut at the front of the car, while a multilink system is used at the rear.

“The benefit is that you increase comfort and at the same time agility,” says Keller. “The chassis is always something of a compromise, but with a double wishbone suspension you reduce that compromise as you can separate forces of steering and damping from each other.” 

Steering and damping are closely linked to lateral forces. The new suspension system is designed to respond with greater precision on rougher road surfaces, giving a better experience for the driver and more comfort for passengers.

At the rear, the lightweight aluminium axle has also been developed to improve comfort. The rear subframe, the swinging arm and three track arms have all been engineered to better cope with the dynamic forces that act on the car.

Not that the previous generation handled badly, but Keller suggests that the suspension set-up had been developed as far as was possible.

“The MacPherson strut was at the end of its development in terms of this vehicle. It’s certainly a very good axle, for example when used on the 3 Series, but for the 5 Series you always need to improve,” he says.

Because Keller was set the target of matching the driveability of the sedan version of the 5 Series, he had to pay particular attention to the weight of the new vehicle and also make sure that the structure was as stiff as possible.

“We put a lot of effort into decreasing the weight. We have aluminium doors and fenders as well as an aluminium hood, and a lot of the front and rear axles are also made from the material,” he says.

That means even though the car is 82mm longer than the previous generation at 2,968mm it weighs between only 1,710kg and 1,800kg depending on the model – 23kg lighter than it would have been had Keller’s team used steel. Changing materials has also improved rigidity by 30% compared to the previous model.

The powertrains available for the 5 Series Touring are the same as those in the sedan. Gasoline variants start from a 3-litre naturally aspirated engine in the 523i, which produces 152kW of power and 270Nm of torque and CO2 emissions of 182g/km with average fuel consumption of 6.5 litres/100km. There is a six-cylinder turbocharged unit in the 535i which produces 228kW of power and 400Nm of torque with emissions of 197g/km while using 7.08 litres of fuel every 100km. The diesel powertrains range from the 137kW, 380Nm unit in the four-cylinder 520d, which emits 135g/km of CO2 with fuel consumption of 4.25 litres/100km, to the 223kW 535d with 600Nm of torque, 169g/km carbon dioxide emissions and fuel consumption of 5.33 litres/100km.