BMW Finds it Hard to Admit that Big & Slim is the Way to Go
by: Martin Schwoerer
BMW's showcase car at the current Frankfurt show is the inelegantly-named "Vision Efficient Dynamics", which sports a number of interesting energy-saving developments. For example, it has a thermo-electrical generator. This converts heat from the exhaust manifold into electric power, which helps to re-charge the batteries of this parallel hybrid vehicle, at a rate of up to 200W. Or, its downsized three-cylinder turbocharged Diesel engine, which supports the two electric motors which are each located on a separate axle. Yet another energy-saving element is active aerodynamics, which allow air into the engine compartment only when it is needed, and creates downforce only at high speeds.
All these developments mirror BMW's philosophy of combining numerous mosaic stones to create an efficient overall package good enough to rival a purely-electric car. Efficient Dynamics indeed, for M3 sportscar performance at a fuel consumption rating of 3.76L/100KM (62.5 MPG US).
BMW seems to be less than sure about one part of its efficiency package, however. Only with difficulty will you find it on BMW's website, but at the Frankfurt stand in Frankfurt, there was this information:
"In order to decrease rolling resistance and enhance the aerodynamics, the BMW Vision Efficient Dynamics is equipped with particularly narrow wheels. Thanks to the larger diameter of 21 inches, however, the contact area is similar to that of a substantially wider tire. the result: greater agility and a high level of safety e.g. when aquaplaning."
BMW is not the first company to envision a future where cars no longer fulfil the macho ideal of fat, wide and heavy wheels. Mindset EV is an earlier concept car whose makers claimed if your wheel size is large enough, you can have really aerodynamic, slim tires without reducing the safety-relevant contact patch. (Mindset has a spectacular wheel size of 22 inches).
The difference between Mindset and the BMW is that the latter hides its narrow wheels behind shrouds. Looking at pictures of the Vision Efficient Dynamics, you'd never guess it has aero wheels. Is BMW afraid of irritating its traditionalist, pistonhead fans? Or is the German company reluctant to admit that some of its innovative ideas are not so new?
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