BMW's 3 Series has always been about the driving. It has many of the attributes of a sports car with the practicality of a sedan. It offers rear-wheel drive and manual transmissions in a class increasingly dominated by front-drive and automatics. Driving has never been much better than the 3 Series, or at least not with seating for five, decent mileage, and a high level of all-season comfort.

The all-new 2006 BMW 3 Series sedans are true to their predecessors, with a couple of caveats. The typical BMW buyer will likely appreciate the technology built into the new 3, and particularly the electronic stability control wizardry. Purists may pine that some of the 3 Series' original purity has been lost.

The heart of any BMW is its engine, and the one in the new 3 Series is first rate. It remains true to BMW's commitment to inline six-cylinder engines, as other manufacturers have switched almost exclusively to V6s. The straight six presents more packaging challenges, but its unique performance characteristics and smoothness make it a favorite among enthusiast drivers. The 3.0-liter six in both the 325i and 330i sedans has the latest in control and materials technology, including the first mass-production magnesium alloy engine block, to reduce weight. It produces 215 horsepower in the 325i and 255 horsepower in the 330i thanks to different tuning, but in both cases it is substantially more powerful than the engines it replaces. It's the first six cylinder without a conventional throttle. Engine speed, and therefore acceleration, is varied by how far the intake valves open. These engines are lighter, more powerful for their size, and more fuel efficient than those in the coupes and convertibles.
In both the 325i and 330i sedans, the engine is fantastic. No one will feel short-changed on performance if they make the more economical choice. Yet particularly in the 330i, the new engine is a pleasure to operate, and it's stronger than any 3 Series engine before, short of the M3. What's best is its linear quality, or the steady supply of acceleration-producing torque at any speed. There's more torque down low than before, but the new engine pulls like a sprinter all the way to its 6800-rpm redline and never misses a step. Moreover, the joy of a straight-six isn't hidden under the high tech. It sounds great, with an emphasis on clean mechanical noise from the engine bay rather than the tone of the muffler.

The new 3 Series sedans come with a choice of six-speed automatic transmission, six-speed manual or BMW's six-speed electro-hydraulic Sequential Manual Gearbox. The manual transmission works great. The shifter seems to have slightly shorter throws between the gears than before, and its operation is appropriate to a world-class sports sedan. The extra gear adds more flexibility to the power band and lowers engine revs at cruising speeds. The automatic we liked a bit less, but it's hardly disappointing. With six speeds, the same advantages apply here as with the manual. The automatic can be a bit slow to react with an appropriate gear change in Normal mode, but leaving it Sport mode pretty much solves the problem without a significant payback in more abrupt shifting. Then there is Steptronic manual mode, which allows manual gear selection by toggling the shift lever to the left. No problem with shift response when you do it yourself.
BMW's SMG (for sequential manual gearbox) won't be available in the 330i sedan until at least September, but we've used it in other BMWs and know how it works. This is not an automatic transmission per se, and if you put an emphasis on smooth shifts, it should not be your choice. While the Steptronic is an automatic with a manual feature, the SMG is a manual with an automatic feature. It has a clutch but no clutch pedal, and in automatic mode it works as if the machinery is working the clutch for you, which it is. In short, the SMG can be great fun, and it works impressively if you're driving hard. If you're puttering about more casually, or even commuting, the conventional Steptronic is far more pleasing. The SMG should be reserved for committed enthusiast drivers.

We found almost nothing to complain about in the 3 Series powertrain; both engine and transmissions work impressively. Yet the other half of the 3 Series equation has always been ride and handling. This is the prototypical sports sedan, or about as close as you can get to sports-car driving dynamics in a practical sedan. For 40 years the 3 Series had defined that mix: rear-wheel drive, great steering feel, and a near-perfect balance between the front and rear axles. Moreover, the 3 had always delivered an impressive balance between ride and handling. The fun never comes at the expense of beating up the passengers inside.
The 2006 325i and 330i sedans ultimately hold true to this heritage as we found on a slick race track in rural Spain. The perfect balance front to rear, the right touch of suspension compliance, the smooth torque delivery is all there, and for the better part of an afternoon we clipped apexes and managed power slides and just had a ball. But we had to turn off all the gizmos to do it.

The new 3 Series suspension layout is borrowed from the larger 5-Series sedan, with double-joint aluminum control arms in front and a five-link fully independent system in the rear. This is trick stuff, but it's nothing compared to the electronics that manage everything. The 3 has BMW's most advanced Dynamic Stability Control chassis electronics yet, with more sensors measuring more things than ever before. It also more aggressively integrates BMW's Active Steering into the electronic stability control scheme.

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Active Steering is optional on both 3 Series sedans, with either the standard or sport suspensions. The idea behind active steering is to eliminate the compromise in conventional, fixed-ratio rack-and-pinion steering: speed the steering up to reduce steering input, or sawing on the wheel, at low speeds, and slow it down at high speeds so a sneeze or a twitch doesn't dramatically turn the wheels and send the car drifting toward a concrete abutment. BMW's active system has an electrically operated transmission on the steering shaft. It reduces steering wheel movement from three turns lock-to-lock in the old 3 Series sedan to 1.66 turns in the new one.
And there's more to the active steering story. The motor that varies the steering ratio is wired into DSC, which measures a bunch of things, including road speed, wheel rotational speed, steering angle, yaw rate and lateral acceleration, as it thinks about what it should do. If some-thing is amiss, say if DSC senses that a particular wheel is loosing traction, it will react by applying the brake at that wheel or reducing engine power in an effort to keep the car going in the intended direction. With Active Steering in the new 3 Series, DSC also can change the steering angle. Not only does it make it easier to park at Macy's or help manage the risks of an arm twitch at autobahn speed. It also helps drive the car by making fairly significant steering corrections without driver input, or even driver awareness, or perceptible feedback on the steering wheel.

All that understood, we still would not check the Active Steering option ($1,250), even if we didn't have to pay for it. The drawbacks outweigh the advantages. For starters, the standard DSC without active steering is more than aggressive enough to help diligent drivers manage a skid. On dry pavement, it's not easy for a reasonably skilled driver to deliberately loop the car. Moreover, on the road the Active Steering mutes some of the great steering feel that has ensconced the 3 Series so firmly in enthusiast drivers' hearts. It's best at high speed, where it feels pretty much like a BMW. Going slower, through seriously twisting back roads, it doesn't. The steering has a lot weight at moderate speeds, but not much feel, and at times it feels too quick. Compared to the 2005 3 Series sedans, it can be more difficult to place the front tires exactly where you want them, and it can be harder to drive smoothly. When slowing aggressively for a slow corner, there can be a perceptible deadness in the wheel as the active steering recalibrates itself.

The same high-tech control capability is built into the brakes, and in this instance we have no caveats. The 2006 325i and 330i have slightly larger brake rotors than the 2005 models. Pedal feel seems slightly different, but it's no problem once a driver gets used to it, and both stopping capability and fade resistance are as magnificent as they've ever been. Now, however, the brake pads move within a hair of the rotors if the driver suddenly releases the gas pedal, even if the driver hasn't yet considered slamming on the brakes. The pads also lightly sweep the rotors every few seconds if it's raining, just to be sure there is no significant moisture build up.