When it comes to respectability in the midsize sport sedan segment, all roads lead through BMW's 5 Series. It's been ruling this class for decades now, and for good reason. It has the uncanny ability to satisfy both driving enthusiasts and buyers who are simply looking for a luxury sedan with German cachet.

Now that the all-new twin-turbo 2011 BMW 550i is here, it was time to see just how well it stacks up against its newest competitors. But instead of going toe-to-toe with a classic European rival, we figured a match-up with the latest from Japan would be more interesting. For that we turned to the all-new 2011 Infiniti M56, a thoroughly redesigned sedan that is once again aiming for the Germans. It has all the makings of a worthy competitor, but how does it hold up on the road?




How They Stack Up
Not surprisingly, the 2011 BMW 550i and 2011 Infiniti M56 have plenty of similarities. Both are rear-drive sedans powered by sizable V8s. In this case, both are hooked to automatic transmissions, a seven-speed in the Infiniti and an eight-speed in the BMW.

To make sure no one whines about "stacking the deck" in one car's favor, both the 550i and the M56 were outfitted with Sport packages. The Infiniti's $3,650 option adds a stiffer suspension with upgraded springs and shocks, larger brakes, Bridgestone Potenza RE050A summer performance tires on 20-inch alloy wheels, four-wheel active steer, paddle shifters, sport seats and a unique steering wheel and shift knob.

The BMW 550i had the benefit of both a Dynamic Handling package, which includes electronic damping control, active roll stabilization (active antiroll bars) and Adaptive Drive (allowing for specific chassis/drivetrain settings) for $2,700, as well as a $2,200 Sport package, which adds a sportier leather steering wheel, multicontour seats, special exterior trim, an increased top speed (limited to 150 mph) and — surprisingly — 19-inch Goodyear Excellence run-flat all-season tires.

Technology and luxury abound in these cars, the kind of niceties that make your drive safer (the BMW's standard adaptive cornering headlights) and more relaxing (Infiniti's standard heated and cooled front seats). Differences come in the form of which features each manufacturer supplies standard, and which ones they make you pay extra for — as an example, you can get those adaptive headlights on the Infiniti, but it'll cost $3,000 as part of the Technology package; conversely, neither heated nor cooled front seats come standard in the BMW — heated seats cost $500 (or could be part of a package), while seat cooling tacks on another $1,950-$2,950 depending on the package.

As you might have guessed, these are expensive sedans. The M56 starts at $58,765 with an as-tested price of $67,130, while the BMW is a few grand more. The 550i starts at $60,575 and our tester topped $70K with options.

What's the Motivation Here?
Turbocharged engines are quickly becoming the norm at BMW, and now the 550i is on board. Its direct-injected 4.4-liter twin-turbo V8 produces 400 horsepower at 5,500 rpm and 450 pound-feet of torque from 1,750-4,500 rpm. Yes, that's a massive torque curve, but it comes at the expense of the old V8's rumbling exhaust. Now there's little more than a muted growl, and you can't even hear the turbos working their magic.

The 2011 Infiniti M56 uses cubic inches and plenty of revs to achieve its power. Its 5.6-liter V8 is good for 420 hp at 6,000 rpm and 417 lb-ft of torque at 4,400. It's no dinosaur, also utilizing direct-injection and variable valve timing and valve lift for a smooth, reasonably efficient power plant.

A little more driver involvement is required to get the most out of the M56's V8, though, as its power is concentrated at higher engine speeds. The Infiniti sounds more like a sport sedan than the BMW, especially when it approaches the 6,700-rpm redline.

By the Numbers
At our test track, the M56 was slightly quicker to 60 mph than the 550i, 5.0 to 5.2 seconds, respectively (4.7 and 4.9 seconds with a 1-foot rollout, as on a drag strip). So the BMW is slower, despite the fact that it's capable of getting a near-perfect amount of wheelspin off the line thanks to power-braking, something the Infiniti's brake-override system won't allow.

So how come the BMW is slower? Might have something to do with the extra 287 pounds of ballast the 4,380-pound 550i carries versus the M56. Seriously, what's a 5 Series doing weighing nearly 4,400 pounds? This is "EfficientDynamics?"

Weight aside, by the time the 550i hits the quarter-mile, its twin-turbo V8 inches the BMW ahead by 0.1 second (13.2 vs. 13.3); it's also traveling a lot faster at this point — 108.3 mph against the Infiniti's 106.7.

A Shifty Pair
The BMW 550i comes standard with a six-speed manual transmission, but our test car was fitted with the no-cost-option eight-speed automatic. BMW says this new tranny's two additional ratios (over the old six-speed auto) come with no increase in size or weight.

It's a smooth operator in full automatic mode and easy to shift when you want to take control of the gears yourself. Not only does it shift in our preferred pattern (forward for downshifts, back for upshifts), it also blips the throttle when you grab a lower gear to match revs. It's not actually a true full manual mode, though, as a stomp on the gas will call up a multigear downshift. It doesn't hold gears either. If you hit the redline, you get the next cog whether you like it or not.

Infiniti offers just one transmission in the M56, a seven-speed automatic with four driver-controlled modes that affect transmission and throttle mappings. As with the BMW, leaving the center console shifter in "D" gives supremely smooth automatic shifting. But moving the center console lever toward the driver puts it in Manual mode, bringing the optional leather-covered, steering-column-mounted magnesium paddle shifters into play. The control is fully with the driver at this point, as the transmission will neither shift up nor down without consent from the paddle shifters. Downshift under braking and it rev matches, too.



These Are Sport Sedans, After All
With all of the BMW's high-techery, you'd think it would easily handle the Infiniti when the going gets twisty. Not so, especially in terms of instrumented testing. The M56 bested the 550i by 1.2 mph through the slalom (66.7 vs. 65.5 mph, respectively) while generating 0.89g around the skid pad against the BMW's so-so 0.84g.

The blame for the 550i's less-than-stellar performance doesn't lie purely with its all-season tires either, as they provided enough grip for it to stop almost as well as the M56 — just 1 foot longer from both 30 and 60 mph. The BMW's pedal felt stronger at the test track, but when pushing hard on back roads the Infiniti's optional ($370) high-friction brake pads felt more consistent.

More than anything, the 550i is simply too heavy and softly sprung for aggressive back-road driving. Even with the suspension at its stiffest setting, the 550i exhibited a surprising amount of understeer, while the 5's electric power steering feels artificial. You can still flog the 550i, but you won't feel completely in touch with the car.

The Infiniti isn't spot-on either. Its variable-assist steering, combined with the optional four-wheel active steering (the rear wheels are turned in phase with the front wheels, depending on vehicle speed and steering angle), makes for overly quick turn-in at low to medium speeds, alarmingly so at times.

But it's clear the driver seat of the Infiniti is the place to be when you pick up the pace on any kind of curvy road. The M56's steering becomes more and more natural as speeds increase, while the stiff suspension soaks up turns, if not bumps, with ease. The whole M56 experience, from its quick steering to its stiff suspension, is a bit on the frenetic side, but it's more engaging than the vague BMW.

There is one area where the BMW trumps the Infiniti on the fun scale — powerslides. Now, the average enthusiast may not find this very relevant, but in the right hands the BMW's electronic limited-slip rear differential does allows you to utilize the twin-turbo V8's prodigious low-end torque to induce some wicked corner exits. And that's all we'll say about that.

When You're Not Laying Rubber
Our enthusiasm for the Infiniti drops slightly the moment the road gets bumpy, or basically any time you're just driving from A to B. The M56's stiff, nonadjustable suspension makes the average commute tiresome and unnecessarily jumpy. The tire and road noise is also a bit much for a luxury sedan, too. Basically, this car reminds you that you bought the Sport package every time you drive it.

The BMW, on the other hand, is always plush and serene. The same sedan that can execute tire-smoking powerslides can also tame mangled city streets. We would still prefer more steering feedback, but the trade-off is slightly less sawing at the wheel during normal driving. It's still a sport sedan, but one you can live with.

No Cabin Fever Here
When you pay around $70,000 for a luxury sport sedan, you expect to be coddled, and neither car disappoints. Both are extremely comfortable places to spend time, the BMW's front seats getting the nod for their width and comfort, the Infiniti's for lateral support.

The M56's rear seat is more plush, while the BMW has more headroom. Fine leather and wood abound, as do such niceties as power rear window shades and excellent navigation systems, the BMW in particular boasting an impressive 10.2-inch transreflective screen that becomes easier to see in direct sunlight — the exact opposite of many systems.

In general the BMW's controls have better detents and are more ergonomic, while the Infiniti's are easier to decipher from the moment you sit in the car. And yes, iDrive Version 4 can still be a bit nonintuitive.

When it comes to interior design, though, the Infiniti has a more interesting take on luxury. The mix of materials in the M56 is more modern and stylish without looking overdone. The 550i has plenty of high-quality stuff; it's just on the sterile side.

And the Winner Is...
As athletic and well-mannered as the Infiniti is on back roads, the BMW 550i squeezed out a win by 2.2 points. Why?

The BMW 550i is simply a better all-around sedan. Infiniti may have figured out the sport sedan piece of the formula, but BMW is better at making a sport sedan that you can live with. We like a tightly wound sedan as much as the next enthusiast, but we don't want to be reminded of the car's capabilities every time we head to the office. It's a fine line for sure, but one the Infiniti still needs to work on.

With the 550i, you get the refined driving experience along with plenty of sport sedan capability. Should it weigh less? Yes. Would we prefer more precise steering? Yes again. The new 5 Series is by no means perfect, but it still puts all the pieces together in a way that makes it feel like a proper luxury sport sedan. The Infiniti is close, but the BMW is already there.

The Infiniti is close, but the BMW is already there.

This comparo is just more of the same and there will be more to come in the future. The REAL question is, who will dethrone the king? I don't mean just 1 or 2 models. I mean become the new standard.

And the Winner Is...
As athletic and well-mannered as the Infiniti is on back roads, the BMW 550i squeezed out a win by 2.2 points. Why?

The BMW 550i is simply a better all-around sedan. Infiniti may have figured out the sport sedan piece of the formula, but BMW is better at making a sport sedan that you can live with. We like a tightly wound sedan as much as the next enthusiast, but we don't want to be reminded of the car's capabilities every time we head to the office. It's a fine line for sure, but one the Infiniti still needs to work on.

With the 550i, you get the refined driving experience along with plenty of sport sedan capability. Should it weigh less? Yes. Would we prefer more precise steering? Yes again. The new 5 Series is by no means perfect, but it still puts all the pieces together in a way that makes it feel like a proper luxury sport sedan. The Infiniti is close, but the BMW is already there.

The Bimmer cost more, has less performance, less stable ride at high speed and less comfort?? Well you know, the wipers and lights control knobs are better......

Not only that....define "drives better"....I did chew more 3 and 5 series that I care of remembering on twisty (often wet) roads with my 6 speed Maxima SE...

They are definitely good cars....just a bit overrated in my opinion...

By the way....do you know when BMW will put something on the road capable of getting at least a bit close to a GT-R?? 3 years?? 5??