The addition of all-wheel drive to the BMW M5 is big news this year. Or is it? The hot-vee twin-turbo S63 V-8 that powers the M5 has motivated 550i xDrive models since 2011, albeit in a civilian-grade N63 state of tune. Now that the motorsports gang has breathed its M magic onto the M550i xDrive, is this xDriven M5 such a big deal?
Read our 2018 BMW M5 Prototype First Drive here.
The M550i xDrive becomes the ninth full-blown M Performance model to reach the market, the total volume of which topped 70,000 globally in 2016. These models slot in above the top-performing regular production BMWs and below the full-on M variants. BMW’s M GmbH establishes the performance benchmarks and designs the body and interior trim modifications for all M Performance models then signs off on the final product to verify that it meets all dynamic targets. The mainstream BMW production departments, however, handle development. So might a carefully optioned M550i xDrive satisfy your ultimate sport sedan needs, or is the M5 totally worth the likely $25,000 upcharge? Having driven both and scrutinized the tech spreadsheets, here’s our take.
Engine: S vs. N
The two versions of this mighty 4.4-liter V-8 are actually pretty darned similar, sharing their 88.3mm bore, 89.0mm stroke, 10.5:1 compression ratio, basic Valvetronic/double VANOS valvetrain hardware, and more. The primary differences that account for the S63 engine’s estimated 144-hp/41-lb-ft difference in peak output are its higher-pressure direct fuel injection system (5,100 psi versus the N63’s 2,900) and larger twin-scroll turbochargers that produce more boost. (Official M5 power, torque, boost levels, and other specifics will be revealed in Frankfurt this September.) Also, although a hard redline is painted on the M550i’s tach at 7,000 rpm, it won’t rev beyond 6,500 rpm, whereas the M5 will rev out to 7,000 or slightly beyond.
Because it’s expected that the M5 will be tracked more than its little brother, the M550i, it features an oil sump designed so that the pump’s pickup never sucks air during sustained high-g cornering. The cooling system is also fortified with a total of nine heat exchangers.
Both cars get larger-diameter, freer-flowing M Sport exhaust systems, and—at least when sampled a day apart—the M550i’s sounds nearly as fabulous as the M5’s. That exhaust sound is a CO2 liability, however. I found myself rocketing away from every 50-kmh village limit in second gear, roaring back up to the 100-kmh rural limit (or slightly beyond) just to please my ears. You also gotta love that the loud-exhaust mode is the default when starting up an M5.
Advantage: Who could argue against 600-plus horsepower and 7,000-rpm redlines? Not us, but the M550i’s engine is super sweet, and if you’re careful to never test-drive an M5, you’ll be delighted with it.
Drivetrain
The M5’s manual and twin-clutch transmissions are both axed in favor of a smoother, more optimally geared ZF 8HP75 torque-converter transmission that is shared by both of these M’ed 5s. It’s largely unmodified from one to the other, with each sharing the same eight transmission ratios while the M5 gets a shorter axle ratio (3.15:1 versus 2.81:1 in the M550i). The M5’s converter locks up after about 3 feet of travel and stays locked. This, along with more rigid mounting of the various powertrain elements, results in greater drivetrain stiffness in the M5. The 7-plus percent shorter overall gearing contributes a bit to the M5’s generally more eager acceleration feel. Shifts under wide-open acceleration with this transmission feel just as quick and crisp as those of the shelved twin-clutch transmission, so save your tears and teeth-gnashing over that box.
Advantage: Basically a tie.
xDrive Guts
The transfer case is also almost identical, featuring a clutched power takeoff that generally biases torque to the rear, but it can apportion front/rear torque from 0/100 to 50/50. In the M5 application the case gets reinforced output flanges, and the front and rear prop shafts are reinforced, though they are still made of steel. But work began on the M5 and its M xDrive all-wheel-drive system after the M550i xDrive was under development, so the M5’s unique unified powertrain/driveline/ABS/stability-control computer with its five drive modes did not get developed for the M550i. Those modes include two with DSC on: full AWD, and M Dynamic mode, which allows slightly greater slip angles. There are also three modes with DSC off: 4WD, 4WD Sport, and RWD. These last three progressively dial back the torque sent to the front wheels, increasing the allowable slip angle accordingly.
Another M5-only feature is the M Active rear differential. Pushing an M5 to its extreme limits on a dry handling track affords a rare and delightful opportunity to feel this differential metering torque across the rear axle. (Note that it is not a torque-vectoring device, but weight transfer to the outside wheel in a turn improves that tire’s potential grip. This diff ensures it gets all the torque it can deliver.) But when pushing an M550i to prudent limits on public roads, you will not miss the fancy diff or multimode all-wheel drive. If you plan to keep and use your car at your track-club condo, you will.
Advantage: Drift kings and folks looking to impress chasing down AMG E63 S 4Matics on the track need an M5. Others will love the M550i.
Suspenders
Relative to ordinary 5 Series cars, the M550i’s suspension gets lowered 0.4 inch and fitted with unique M-spec bushing, spring, and damper rates that are upgraded even relative to M Sport packages on lower 5s. Standard 19-inch or optional 20-inch M-design wheels in a “Cerium” finish (which looks like titanium) are available with M Performance exclusive Michelin Pilot Super Sport tires. The M550i’s standard electric power steering gets M-specific Sport and Sport+ mode tuning that is essentially shared with the M5 (making this the first M5 with electric power steering). The feel coming through the rim is quite different in the two cars due to the different rates of suspension response, with the M5 seeming to turn in more crisply. Active roll stabilization and rear-wheel steering are available on the M550i as part of the $3,600 Dynamic Handling package (which also includes adaptive shocks), but they are not offered on the M5. The big dog’s inherent cornering demeanor negated the need for the added weight of these systems. M Sport brakes with metallic blue calipers and M badging round out the package.
Buy an M5, and you get revised suspension kinematics courtesy of unique front and rear lower lateral links and rear toe-control links. You’ll also get M-tuned bushing, spring, and damper rates. Next-gen ZF damper valving offers more variability in jounce/rebound tuning and utilizes aluminum shock tubes instead of steel. There’s also a unique cross-car X-brace to reinforce rear suspension mounting points, and the brakes are further upgraded (with the option of carbon-ceramic discs, of course).
Advantage: Not surprisingly, the Comfort mode setting of the M5 seems better at making it more drivable on a black-tie double date than the M550i’s sportiest setting does at transforming it into a weekend track star, but then again, is either of these big sedans really an ideal track-time candidate?
Body
Relative to pedestrian 5s, the M550i gets more aggressive-looking fascias, an M aerodynamic kit that includes a lip spoiler on the decklid, Shadow Line gloss black window trim, more of that Cerium Grey metallic trim on the exterior mirror caps, the kidney grille frame, the front air intake trim, and two front fender vents.
M5s get even more aggressive-looking fascias with nostrils flared wider to cool all those heat exchangers, a slightly larger lip spoiler, a unique power-bulge hood, wider fenders and quarter panels, and a carbon-fiber roof panel that’s new to the M5.
Inside, the M550i gets standard multicontour seats upholstered in black Dakota leather with blue contrast stitching (Nappa leather is optional), plus the latest version of the M sport steering wheel, M-design floormats, and aluminum pedals. Again, the M5 dials all of that up to 11 with fancier, more highly bolstered front seats featuring articulating backrests.
Advantage: How highly do you value subtlety? The M5 appears to be beating its chest and daring folks to race it, whereas the M550i’s bravado is a bit more chill.
Bottom Line
The M550i xDrive is one helluva fun car for blasting around hilly, twisty Bavarian back roads. Yes, it’s a less extreme performer than the M5, but what, maybe 17 percent less extreme? That’s a deal worth considering, given the expected 25 percent base-price reduction. And OK, if you equalize the equipment as much as possible by optioning up your M550i with the Dynamic Handling package ($3,600), the 20-inch M double-spoke wheels ($950), and the head-up display (sold in a $1,700 driver-assistance package), that discount drops to 19 percent. It’s still well worth considering—especially because you can get it now instead of waiting until next March.
| 2018 BMW M5 | 2018 BMW M550i xDrive | |
| BASE PRICE | $98,000 (est) | $73,095 |
| VEHICLE LAYOUT | Front-engine, AWD, 5-pass, 4-door sedan | Front-engine, AWD, 5-pass, 4-door sedan |
| ENGINE | 4.4L/600-hp (est)/520-lb-ft (est) twin-turbo DOHC 32-valve V-8 | 4.4L/456-hp/479-lb-ft twin-turbo DOHC 32-valve V-8 |
| TRANSMISSION | 8-speed automatic | 8-speed automatic |
| CURB WEIGHT | 4,300 lb (est) | 4,000 lb (mfr) |
| WHEELBASE | 117.1 in | 117.1 in |
| LENGTH X WIDTH X HEIGHT | 195.4 x 73.5 x 57.8 in | 195.4 x 73.5 x 57.8 in |
| 0-62 MPH | 3.4 sec (mfr est) | 4.0 sec (mfr est) |
| EPA CITY/HWY/COMB FUEL ECON | Not yet rated | 16/25/19 mpg |
| ENERGY CONSUMPTION, CITY/HWY | – | 211-135 kW-hrs/100 miles |
| CO2 EMISSIONS, COMB | – | 1.02 lb/mile |
| ON SALE IN U.S. | March 2018 | Currently |
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