It's the biggest, baddest Pontiac sedan in the fleet, a company flagship since the Bonneville name first appeared in 1957 on a top-of-the-line convertible.

And for the first time in 18 years, the Bonneville has a V-8 under its hood, along with a base and uplevel V-6 version seen in this Wide Track for the past few years.

So we tested it for a day on the industrial streets of Indianapolis just weeks before Sunday's Brickyard 400 NASCAR race, while doing a story on the Hall of Fame Museum and famed race track for Sunday's Travel section of the Times-Union.

The cleaner, leaner Bonneville received its last major update in 2000, the first since its last edition was redone top to bottom in 1992. The 21st-century version included the stiffest chassis in the company at the time with a 62 percent increase in torsional stiffness, on a wheelbase stretched two inches. But the car still had the dreaded ribbed side cladding, a holdover from the bad old days of the 1990s.

Well, we are pleased to say the 2004 Bonneville GXP we tested for the day is finally ribless, with a tighter, tauter design first seen on the Pontiac Grand Prix a year ago.

The Bonnie comes in three modes -- 205-hp SE and SLE, with un-supercharged V-6s, and the 275-hp GXP with a 4.6-liter, DOHC 32-valve Northstar V-8. The base SE still has a bit of the ribbed-side design, while the SLE gets slight hints as well as nose design with big round fog lights, not unlike the supercharged SSEi version we tested a few years ago -- a bit of overkill, we think.

The new GXP goes on the ribless diet, starting with the cleanest nose design of the three. The traditional split kidney grille is there, with a Pontiac emblem on the edgy design line that runs down the middle of the big hood. Two under-bumper inlets get faired-in fog lights, while the side cladding is shrink-wrapped to the flanks, the sill edging out for some visual tension between flared fenders that frame five-spoke alloys that show the red-painted disc brake calipers front and rear and Goodyear Eagle RS-A P235/50R18-inch radials. The flush body-colored door handles ride on the soft remains of the pinched waist design the Bonneville has carried for a decade and more, while the roof line plunges aft to rounded rear fenders with expressive taillights and quad exhausts framed by a gray rear apron. The car looks lighter and tighter, while retaining some of the slightly cartoonishly sporty look Pontiacs have been known for.

If the exterior is leaner, the dark-gray-over-light-gray interior is still the gee-whiz rounded wonderland shape Pontiacs have been known for. The driver faces 58 buttons, knobs and switches, not counting six on the steering wheel and stalk and more overhead -- most backlit in the red/orange we've seen in Pontiacs for years.

The driver and passenger sit on sculpted gray leather bucket seats with lighter gray suede insets, both with power adjustments, the driver getting height-adjustable power lumbar, power seat back adjustments and twin memory presets. They were comfortable, but lacked side support despite aggressive-looking bolsters. Brushed aluminum accents the door handles and gearshift, while some pretty convincing fake carbon-fiber trim trims the doors, air vents and dash center.

The sweeping gauge package is easy to see through the meaty four-spoke, leather-clad, tilt-adjust steering wheel, its half-circle centered on a big 160-mph speedometer and 7,000-rpm tach with temperature and fuel gauge in between, and oil and voltage on either side. A digital odometer/tripmeter sits to the right, partially hidden by the steering wheel rim, followed by a driver information screen. Its buttons complete the sweep of the gauge package, while two of eight adjustable vents encased in fake carbon fiber nearby.

More rounded buttons and rubber-coated knobs greet you underneath, with a great-sounding eight-speaker Monsoon AM-FM-XM Satellite-CD-Cassette deck, and a dual-zone climate control system at the bottom. The traction control button is buried down there. Twin cup holders occupy the curved center console, with adequate storage under the padded center armrest. The glove box was decently sized, as were the map pockets under ribbed grab handles and suede inserts. The head's-up display showed the speed, stereo and other functions at the base of the windshield -- a good idea, but sunshine faded it out. And the windshield washer system, with full tank, wouldn't pump.

Access to the rear seat was OK through the rounded doors, and we found decent head and leg room there despite the sunroof, although the bottom cushion was low. Twin air vents sit at the rear of the GXP's center console, as does a small ashtray and 12-volt outlet, while the center armrest has two cup holders. There was a ski pass-through to the huge trunk, which contained a net for storing small stuff.

Now, we talk about the fact that this Bonnie packs a V-8 for the first time in years, albeit one connected to front-wheel-drive and not the rear wheels as the first three decades of big Pontiacs had. Normally a 275-hp Cadillac engine, this aluminum, DOHC, 32-valve powerplant gets the same ponies, 300 lb.-ft. of torque and a snarling exhaust note. But is it any faster than the supercharged 240-hp V-6 we tested in a 2000 Bonneville SSEi?

The supercharged V-6 got to 60 mph in 7.5 seconds. We launched our 4,600-mile V-8 GXP to 60-mph in a tenth-second less, wheelspin reined in by traction control. We managed only 15-mpg according to the trip computer, and it needs pricey premium.

As far as ride, the Wide-Track Pontiacs of the '50s and '60s are back with the GXP, whose four-wheel independent suspension offered a firm-yet-comfortable ride that easily swallowed pavement cracks and didn't beat you up, while controlling the heavy car well. The car remained quiet and flex-free, a tribute to the stiffer design, while the car cornered fairly well with minimal understeer. You feel the weight of the car, but it is stable and comfortable, a confident handler for its size. The StabiliTrak electronic stability system handled wheelspin and understeer in the rain, while the Magnasteer power steering had a direct if slightly numb feel in the twisty bits. The four-wheel anti-lock disc brakes hauled the car down well with minimal nose-dive and no fade after repeated hard use.

The base (,690) V-6 Bonneville SE gets standard cruise control, power door locks, remote keyless entry, rear-seat pass-through, AM-FM-CD stereo, alarm and power windows with an express-down feature for the driver and front passenger. The up-level (,540) SLE adds a standard driver information center, 17-inch five-spoke aluminum wheels, traction control, heated power exterior mirrors, a 3.05 performance axle ratio and a rear deck spoiler.

Our GXP started at ,270, with the 275-hp V-8, front and side impact air bags, alarm, remote keyless entry, 18-inch alloy wheels, rear spoiler, eight-speaker Monsoon AM-FM-CD stereo, leather and suede seats, OnStar and express-down driver and front passenger windows. The power sunroof/HomeLink garage door opener added ,100, the 100-channel XM Satellite Radio , and head's-up display another . With destination fee, the big sports cruiser's manufacturer's suggested retail price was ,745.

Bottom line -- except that other V-8 full-size sedans in this class from Jaguar, Mercedes-Benz, Dodge/Chrysler, Lexus and Infiniti all have the power going to the rear wheels, the Bonneville GXP has about the same room, equipment level and handling capabilities. It looks sleek and more business-like, its design showcasing the simpler edgy look of the recently redesigned Grand Prix and upcoming G6.

But as nice a sedan as the GXP is, Pontiac needs to simplify the overdone interior as it has the exterior, and get on the bandwagon with a new rear- or all-wheel-drive Bonneville if it really wants to be a sports sedan leader at a nicer price than most of the competition.