Steer Me, Feel Me: Exploring Why BMWs No Longer Excel in Steering Feel

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Car and Driver’s affection for BMW sport sedans has cooled during the past five years as the Bavarians shifted focus from hard-core driving enthusiasts to their growing throng of luxury customers. The unfortunate side effect is diminished emphasis on the attributes we prize: an astute balance between a supple ride and laser-sharp handling, impeccable braking, and—most significantly—a clear and concise dialogue between the driver and the road through the steering.

To air our grievances, we met with BMW driving dynamics expert Johann Kistler. While his current assignment is Project Director for the new 2017 BMW 5-series due for introduction later this year, Kistler guided development of the last two generations of 7-series sedans and was responsible for the move to electric power steering (EPS) for the current (F30) 3-series introduced for the 2013 model year.

Kistler began our conversation on the Car and Driver wavelength—by reflecting on the 1974 BMW 1602 owned by his wife: “This is her favorite and quite an amazing car.”

“That car is what we started with, all the feedback you can get. There’s no support (power assistance) so you have a lot of force. To remedy that we added hydraulic assistance and you get all the messages from the road delivered to the car. That means good information and bad information. When we moved to EPS we learned how to divide the good and the bad messages for the customer.”

Asked to cite an example of bad information, Kistler explained, “Lines in the road with an orientation parallel to the car’s path cause what we call ‘pull drift.’ The tires try to follow the lines instead of the direction selected by the driver through the steering wheel. While that’s difficult to address with hydraulic power steering, with EPS we can install what we call pull-drift compensation to help keep the car locked on a straight path, instead of following longitudinal grooves.

“We’ve learned a lot about refining EPS since it was introduced four years ago. One is a new calibration philosophy that allows easy adjustment of the required steering torque. This makes a major difference in the feel of the new 5-series. There would be no chance to match those results with hydraulic assist.”

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Attempting to shift the focus from steering effort to the feedback routed from the pavement to the driver’s hands, I asked if any EPS strides had been made in that specific area. Kistler responded, “We surveyed both current BMW 5-series customers and owners of competitive models, asking ‘What are your wishes.’ We have two million customers around the globe who’ve purchased the 5-series during the past 5 years, which results in a broad spread of demands. Our job is to fulfill those mainstream needs.

“There was a clear request for less steering effort. No one wants bad feedback—such as a steering wheel that vibrates in response to bumps in the road.”

I pointed out that few customers speak the engineering language we use to describe this area of car design. As a result, when the subject of steering is addressed, the most common thought popping into their heads is how easy the car is to park. The fear among driving enthusiasts I shared with Kistler is that BMW is now heading in the Lexus direction (and some Lexus models, such as the IS sedan, are much closer to BMW’s former steering tuning). And what enthusiasts pine for is the steering feel from an earlier generation, when the rack-and-pinion system was hydraulically assisted.

“It’s not our intention to go the Lexus way. We expect to be the sportiest example in every car class we compete in. This is the BMW way. We do study how competitors tune their cars but the goal is always to deliver authentic BMW driving pleasure.

“One current priority is reduced weight. We work hard on the suspension, the steering, and the engines—all crucially important to the character we’re seeking.”

“The real challenge was reducing the effort without diminishing feedback. We used new simulation methods to model and optimize the body structure. Collaboration between the chassis and body experts helped perfect the suspension connection points. We also simulated suspension kinematics and learned a lot from that.

“With the next generation of run-flat tires, we reduced their driving range to 50 miles to lower sidewall stiffness and its negative effect on ride and handling. The goal was lower steering effort with better information from the road. We call this development, beginning with simulation and ending with final driving refinement, mechanical integration.

“The area we call mechatronics encompasses the electronic systems interconnected by data communication—brakes, variable dampers, and four-wheel steering. A team uses computer software to integrate these parts of the car.

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Without specifically discussing our complaint that feedback has been missing since the arrival of EPS, Kistler shifts the conversation to steering precision. In this specific area BMW still excels. Following turn in, the effort builds nicely and no steering wheel adjustment or correction is necessary to hit and hold the desired arc.

I force his thoughts back to feedback—the subtle information about how hard the tires are working, whether they’re approaching the adhesion limit, and specifically what’s going on where the rubber meets the asphalt.

Kistler responds, “translated to German, the English word ‘feedback’ encompasses the car’s precision, how quickly it responds, basically everything the car does. It’s a large cake while what you’re addressing is one thin, specific slice.

“My personal opinion is we’re providing enough feedback to our mainstream customers. Some drive 30,000 miles per year in their BMWs, including long trips at high speeds. So the strongest demand we heard was ‘Please reduce the steering effort.’ They seem to want more isolation.”



Then Kistler asked if I believed any current BMW provided the feedback I expected. When I answered no, he asked if that included current M models, especially the M2. I reported our deep appreciation of the M, sharing specific comments from our test of the car and our disappointment in that car’s distinct lack of feedback.

Asked for an example of some current EPS car that offered what we’re seeking, I nominated the current range of Porsches—Boxster, Cayman, 911, even the Macan.

Kistler did show appreciation for our frank discussion. He concluded the conversation with a promise to focus on learning more about this issue, “We have many BMW fans in America. It’s worthwhile to me to understand and to meet their demands. So I will take your feedback concerns with me and think about them. And I will discuss with my team how we can move in this direction with sacrificing other customer benefits.”


from Car and Driver Blog http://blog.caranddriver.com/steer-me-feel-me-exploring-why-bmws-no-longer-excel-in-steering-feel/

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