If you know the BMW 5-Series, you could almost hear the gasp going out when word spread the Bavarian automaker was looking at making a few tweaks and a few tucks for 2004. Change it? Inconceivable. Make it better? Impossible.

How do you improve a ride that was named a 10-Best winner by Car and Driver magazine six years running?

You could almost hear the rumblings from the BMW faithful firing up like a six-cylinder engine.

When it comes to ride, handling and performance, it's no secret the fourth-generation 5-Series has been both the bench and the mark. It has set the standard for luxury sport sedans. It has attracted more and more paying customers every year from 1996 through 2002 - defying convention by achieving even higher U.S. sales in its final calendar year. For seven years it has been the standard.

So why redesign? BMW says because it "knows how to follow tough acts." Just make them tougher.

We're here to say, the old champ hasn't lost its crown.

Three new models will be phased in next month, forming the new-generation 2004 5-Series - a roomier car that arrives longer, wider and taller than ever before. BMW says the gains in dimension will result in greater rear-seating space, more comfort and a bigger trunk.

Big news? You don't know the half of it.

But just when you thought the 5-Series might get too large around the middle, BMW says it promises to stay fit and trim where it counts. And there it really scores.

Really, it's all about carrying a good weight. Driving feel, maneuverability and agility have always been core values of the 5-Series and in the new model that theme continues mainly thanks to an all-aluminum front-end and chassis. It means an increase in size as well as advances in comfort and safety with decreases in overall vehicle weight.

But the largest shift, the biggest news, comes in the form of technology. Are you ready for this? Is the competition?

Several items are being pulled directly from the recently redesigned 7-Series, including: iDrive, the central nervous system for the climate, audio and navigation controls that is standard on the 5-Series; Active Roll Stabilization, a traction control system that senses a possible rollover and then prevents it; Active Cruise Control, a brain on board that keeps the 5-Series a safe distance from other cars on the road; and a Harmon Kardon Logic 7 sound system.

But this isn't some scaled down 7-Series, BMW's biggest sedan. But it is enough to make you think you're riding on the space shuttle.

Several advanced technologies make their debut on the 5-Series for 2004, including BMW's much-anticipated Active Front Steering. The AFS system varies the level of steering input a driver must use in direct relation to the style and speed of driving and road conditions. For example, under normal conditions at low and medium speeds, the steering becomes more dire ct, requiring less effort from the driver (turns of the wheel) and increasing agility in city driving and parking.

It's downright remarkable. In tight, twisty turns, your hands never have to adjust on the wheel. In a straight line, it feels rock solid.

One note: More than once, after slowing down from highway speeds to make a turn, I initially used too much input on the steering wheel. But I think with enough time, that will come.

And the technology continues. Additional features that debut on the 2004 5-Series include optional adaptive headlights that rotate to illuminate the road ahead in a turn and adaptive brake lights that will brighten the taillights when the driver applies extra pressure on the brake pedal, giving additional warning to following vehicles that hard braking is taking place. And there's even an optional fold-down DVD player for rear-seat passengers.

If all of this has you thinking the new 5-Series is nothing more than a giant computer game, think again. BMW hasn't forgotten there is still a sport in sport sedan.

The new Series consists of three models, each powered by its specific engine. The 525i sedan continues with the engine of its predecessor, the responsive and fuel-efficient 2.5-liter, 184 horsepower inline six-cylinder that belies any thought of "entry-level" status; the 530i offers a step-up in six-cylinder power with a 3-liter, 225-horsepower engine and additional standard equipment over the 525i; and the 545i sedan which derives its new model designation from the Vakvetronic engine first introduced in the 7 Series - a 4.4-liter V-8 delivering 325 horsepower, up 35 horses from the previous 540i.

Each model is available with a choice of three transmissions, all six-speeds: manual; Steptronic automatic and a manual Sequential Manual Gearbox (SMG) that allows clutchless shifting.

Each model flies. It is pure BMW guts and grunt with the refinement perfect for an Autobahn - if we had one, which might be the most frustrating thing about the 5.

From the outside, design czar Chris Bangle - he of the redesigned 7-Series fame - has added his "flame front" styling, making the 5-Series a more sleek ride from curbside. It is bold. It is daring without losing the 5-Series' trademark stance. It is gorgeous. Crisp lines flow from the front to the back, making it appear elegant yet sporty.

Inside, the upgrade allows for greater rear-seat roominess, expanding the 5-Series into a truly 5-person ride. And have we mentioned the tech stuff enough? There's an optional multi-colored heads-up display, a wireless communication system than can link the car's hands-free phone with the customer's own cellphone. And the air-conditioning monitors the humidity level. The humidity!

On the negative side, the iDrive central computer is still a work in progress. In the 7-Series, rumor had it many older owners were taking their cars back to the dealer asking for a refund because the system was just too complex. This is easier - the main menu now controls only four categories (navigation, communications, climate control and entertainment) - but it still requires a day to figure out.

And the price will probably edge up a bit - $39,995 for the 525i sedan all the way up to $58,295 for the 545i six-speed. That's serious territory in the high end but, on the whole, BMW's best-selling sedan is still the benchmark and more. Still the luxury sport sedan it always was. Still the Ultimate Driving Machine.

Fear not, 5-Series lovers. Fear not.

2004 BMW 5-Series

Rating: 4

High gear: With enough technology to launch a rocket, and a rocket of an engine underneath the hood, a good thing gets better. The new 5 offers more length, width and height without sacrificing the essentials: handling, performance and style.

Low gear: Some of the technology can be a little overwhelming and take a while to get used to. Price becomes an issue in higher end models, but that's expected in this segment.

Vehicle type: Rear-wheel-drive, front-engine, four-door, five-passenger sedan.

Key competition: Audi A6, Infiniti M45, Lexus GS 430, Cadillac CTS

Base engine (525i): 184 horsepower, DOHC 24-valve 2.5-liter inline six-cylinder

Torque (525i): 175 lbs.-ft. @ 6,000 rpm

Standard safety equipment: Four-wheel anti-lock brakes, driver and passenger front air bags, side air bags, tractional control, stability control, advanced Head Protection System to protect occupants in side impacts, front-seat safety belts with automatic tensioners and force limiters.

Wheelbase: 113.7 inches

Length: 190.6 inches

MPG rating: 17 city/31 highway

Manufactured: Germany

Warranty: Basic warranty is four years/50,000 miles; drivetrain is four years/50,000 miles; roadside is four years/50,000 miles; and rust is six years/unlimited miles.

Base price (525i): $39,995

Price as tested (including options, delivery and destination charges): $40,690