2005 BMW 530 Preview

The New BMW 5 Series

The Ultimate Driving Machine handles even better, but what about its looks?

Engineering

BMW has to be careful about new technology. More than the case with other carmakers, BMW's buyers identify with the way the cars drive -- not just look. The plain truth is that if you're rounding a bend at nose-bleeding g's, you're not apt to care about the shape of a headlamp. But if you can't drive your BMW confidently around a bend at nose-bleeding gs, or if the car steers too lightly, or loads up unpredictably, or its in-line six-cylinder engine revs in less than linear fashion.... Well, then, suddenly it's no longer a BMW.

Which makes the introduction of Active Steering in the new 5 series a potentially more dangerous decision than anything Chris Bangle could have done with design.

OK, so what is Active Steering and why would it be controversial? First, what it's not is so-called steer-by-wire, so there's no mechanical link between the steering wheel and front tires. Rather, there is the same rack-and-pinion setup as there has been in the past, but in this case BMW has added a mechanical planetary gear set to the steering column.

Eyes glazed over yet?

OK, cutting to the chase, what Active Steering does is alter the number of revolutions it takes to turn the wheel, depending on the speed of the car. At five mph, when trying to parallel park, it only takes two turns from far left to far right (aka "lock to lock"). That makes parking a snap because your hands don't have to cross over nearly as many times. But at 100 mph the effective number of turns lock to lock is about 10, greatly increasing high-speed stability and eliminating the jitteriness you'd otherwise feel in the wheel if the number of turns lock to lock were fixed at, say, three.

The real magic in the system, however, is that it can actually function as a counter-steering mechanism in a tight turn. That is, when driving the 5 through switchbacking mountain roads, Active Steering (via an electronic yaw sensor/steering-angle sensor connected to the power steering) will "read" the amount of slide force at the wheels, the available traction and whether the car is apt to plow wide of where you've pointed it and actually increase or decrease the steering angle to keep the car on course.

Ah, and now you see why this might be controversial -- the car might seem as if it's steering itself. The reality is, that's not the sensation at all. Rather, instead of having to row the wheel back and forth through sharp bends, the need to "correct" for too steep an initial turn in (say, when the rear end of the car dances out a bit) is completely eliminated. As soon as you begin to snap the wheel back to center, it's already anticipated your input and straightened the car out.

Further helping this remarkable, newfound steering agility is a new system for the 5 (already debuted on the 7 series) called Active Roll Stabilization. (It's available only with the Sport Package on U.S. models; see the Bottom Line section) This system allows greater articulation of the car's suspension when driving under low-yaw circumstances (driving relatively straight) to soak up bumps, but much more rigid response the harder the car is driven through turns.

Two "active" anti-roll bars (one at each axle) are connected hydraulically to sensors and, when cornering forces are applied, convert the pressure into suspension/chassis stabilization. This eliminates the tilting forces that make both driver and passenger feel a little seasick after a lot of mountain- or coastal-road driving.

Bottom line: ARS yields less sway during sporty driving and a more placid, forgiving ride during everyday driving.