High Plains Drifters: 2006 BMW M5 vs. 2006 Mercedes-Benz CLS55 AMG

Motor Trend

21-07-2025

`[This story originally appeared in the June 2006 issue of MotorTrend] There's something wrong here--and so right it hurts. A two-ton sedan shouldn't do the things a world-class sports car does. Want to pass that piece of rolling road furniture parked in the fast lane? Bam! It's gone in as long as it takes to turn your head. Care to shake-off those tailgating Tooner Boyz on the freeway interchange? Whoosh! Your satisfaction will arrive at the same moment they realize there isn't a hope of matching your cornering speed. Oh, hello, officer. These are my vented and cross-drilled brakes, which can haul me down to a safe and sane rate of progress (120-to-60 mph) in less time (2.6 seconds) than it took for you to notice. The officer removes his sunglasses, peruses the vehicle, and says, "You're not exactly driving a Corvette or a Carrera."
The 2006 BMW M5 and Mercedes-Benz CLS55 AMG are powerful sedans. The M5 offers a more engaging driving experience with 279 settings, while the CLS55 is smoother and easier to drive.
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Behold the undisputed state-of-the-art super sedans: The 500-horse V-10 BMW M5 and the 469-horse supercharged V-8 Mercedes-Benz CLS55 AMG, the latter having just dusted off Caillac's latest attempt to play in this arena with the STS-v (January 2006). Brought to you courtesy of a cross-town rivalry as intense as Bow Tie versus Blue Oval or Prancing Horse versus Raging Bull, the M5 and CLS55 pack as much power as they do panache. Should a 500-horse four-door sedan shootout surprise you? Probably not, but you can't deny it's a milestone worth celebrating with a dawn raid of the infamous El Mirage dry lakebed.`
Which is faster? That depends on the M5's state of readiness (it boasts an astonishing 279 combinations of selectable performance parameters within the engine, transmission, suspension, and stability/traction control settings); the skill of the M5's driver--assuming warp drive is selected; and, finally, on what's meant by "faster." Note the two acceleration data columns for each car (see sidebar): "optimized mode" and "default mode." For an optimized acceleration run in the M5, this means four selectable combinations programmed into the car's MDrive menu (viewed on the iDrive screen), which can be called up at the push of the steering-wheel-mounted "M" button. Trust us, you'll come to love the "M" button.
Full commando settings programmed in this test for the ultimate M5 launch? P500 Sport power and throttle response (500 horse and quickest response); S6 transmission (fastest/hardest manual shifts. The only transmission currently available for the M5 is a new seven-speed SMG automated-clutch manual with six pre-programmed shifting strategies ranging from slow/smooth to tire-chirping hard. BMW promises a traditional six-speed manual with a clutch pedal by fall 2006); sport Electronic Damping Control (firmest); and deactivated Dynamic Stability Control (which includes shutting down the traction control, required to access the transmission's S6 mode). Once these criteria are met, a quick stab at the throttle pedal with the other foot off the brake launches this rocket (sans a "launch-control" button), which brings the revs up between 3000 and 3500 rpm before the clutch drops and wheelspin ensues.
Backing out of the throttle just enough to keep forward progress, but not so much that the car falls out of the powerband, will leave two dark patches on the way to a quick 0-to-30 mph of 2.0 seconds. Like running up a playground slide in your socks, it's a lot of work, but entertaining work to be sure. Pulling the shift lever once at redline nets 60 mph in 4.5 seconds, and twice more finds the quarter mile in 12.9 at 114.9 mph. A traditional clutch would make the launch far easier to perform, but the advertised 0.65-second shifts would be difficult to replicate.
In contrast, the M5's default startup settings P400 (400 horse), D3 (moderate-speed automated shifts), EDC "comfort," and DSC "on" (including traction control) resulted in a 6.0-second 0-to-60 time and 14.4-second/101.9-mph quarter mile. Why? BMW claims that a car built to the outer edge of the M5's performance envelope doesn't make for a daily driver, hence the multi-modes and the M-memory button. The two combinations for acceleration selected here are close to either end of the car's spectrum. But remember: It take only the push of a button to access the dark side of the M5's personality.
In the CLS55, there are just three button options (or 18 combinations): Electronic Stability Control including traction control (on or limited), Airmatic suspension (Comfort, Sport 1, or Sport 2), and SpeedShift automatic transmission (Comfort, Sport, or Manual). The optimized mode consisted of ESP off, Airmatic Sport 2, and Speedshift Sport. Default settings revert to those last selected but ESP reengages. For comparison purposes after the optimized run, Comfort settings on suspension and transmission with ESP on were tried, resulting in effectively identical runs, varying by just 0.1 second across the chart. At its "slowest," 60 mph arrives in 4.5 seconds on the way to a 12.8-second, 113.5-mph quarter mile. In other words, the CLS55's Comfort mode narrowly beats the M5's full-tilt-boogie up to 100 mph where the M5 gradually makes the pass.
But there's so much more to these two cars than drag racing. At some point, when it becomes prudent, one forgets the size (and sizeable price tag) of either one of these cars and just drives the living cheese out of them. With the M5 in full battle mode, it attacked the cones in figure-eight and slalom tests with sports-car ferocity. In just the first pass, normally at a "getting-to-know-you" pace, we underestimated the slalom speed by more than five mph. It's hard to comprehend an entry speed indicated at over 70 mph in a sedan, but that's how an average of 67.7 mph comes about.
The steering is near-perfect, weighted and lively on-center and providing a generous amount of bite and feedback as the wheel turns. The M5 utilizes a variable-ratio system that isn't the company's Active Steering, as you know it. Rather than varying the ratio by vehicle speed (which mucks things up on decreasing-speed corners like in the figure-eight test), it instead changes to a quicker ratio as the steering wheel is turned away from its centered position. Only the resistance varies with the vehicle's speed. Together they work to deliver unambiguous signals to the driver who can make minute adjustments or heroic opposite-lock slides with equal confidence.
On the limit, few cars we've tested can match the M5's athletic bearing and invincible disposition. It exists to please, to challenge, to deliver, and to incite a good driver to be a bad boy. It's not perfect, though. In the figure-eight, the SMG transmission sometimes ignored the request for a 3-2 downshift when traveling faster than second-gear's upper rev limit. The fact that we were deep into the ABS, decelerating through the computed limit (about 66 mph), didn't usher the gear change (even a delayed one) once we'd gone below that speed. You quickly learn the computerized system can make a velvety-smooth downshift mid-turn without upsetting the chassis. Neat, but you'd rather ask once for a downshift.
While we've already tested a number of CLS-class cars, none was as willing to dive into the slalom test as this particular CLS55. ESP's inevitable tug on a front brake was anticipated as the prescribed limit of the stability program's parameters was approached, but it seemed nearly absent this time around. For the first time, the limits of tire adhesion and suspension compliance with the system in its "off" (actually limited) state could be probed.
That we improved our slalom speed for a CLS55 by nearly two mph, a significant amount, says that we've either learned how to play more smoothly within the limits or that the ESP program now allows more play in general. The latter is most likely true due to the car's permissiveness to do 50-mph drifts on the dry lakebed--for the benefit of the photographer, of course. The fun was spoiled somewhat by the brittle, oddly disconnected steering that feels over-boosted at speed. It could benefit from a quicker ratio, but there's something other than tuning, more mechanically or linkage-related at play here. It just doesn't disappear from your consciousness as a control like the M5's steering wheel does. Still, the CLS55 engine's low-end and the slight lateral g-loading advantage helped it eke out a narrow lead over the M5 on the figure-eight course. Where the M5 is nimble and enthusiastic in the high-speed slalom, the CLS is solid through the figure-eight's corners and more aggressive on their exits.
On the highway, both cars' three-way button-adjustable suspensions offer an equally useful range of comfort or sportiness. They can soak up miles of Interstate or slash through mountain passes with the facility of a car having a multiple-personality disorder. However, the Mercedes was less able to isolate tire thrum and vibration, especially on aggregate surfaces. Both feature suitably aggressive seating that also works on a long haul.
Fundamentally, the M5 is sobering and intoxicating. It sounds the way you might imagine a smaller-displacement, freer-revving Dodge Viper V-10 would, and yet the M5's 5.0-liter engine matches the Viper's output with 3.3-liters less (or the size of a typical V-6) displacement. Rev it up, and the M5 barks a 10-part harmony a Viper never has or ever will. Operating this car is an exercise in restraint; that "M" button taunts you. The way the M5 involves, entices, and rewards is uncanny despite its size--especially for its size. While 279 combinations of button-pushing seem like a "because we can" statement, or because BMW couldn't decide on what vehicle settings to make standard, the flexibility is useful. 1st Place: 2006 BMW M5
Dial M for magnificent. An iron fist in a titanium glove with a computerized conscience to keep you from getting in trouble every time you start it up.
The CLS55 is like Hulk Hogan dressed for a cocktail party: Its elegant exterior belies the muscle-bound tough guy within. With all its effortless power, it feels as if it's being drawn faster to the horizon by an electromagnet. The ultra-smooth transmission only enhances the CLS's (Corporate Luxury Shuttle's) AMG (All Mighty Grunt) power. The fact that it's just as fast as the M5 but requires less driver involvement for less handling prowess will no doubt appeal to many, more often. 2nd Place: 2006 Mercedes-Benz CLS55 AMG
Point it and plant it. Elegantly languid looks belie headbanging straight-line grunt, but it feels more one-dimensional.
This battle boils down to a choice between a fighter jet or luxury jet. Do you want to configure your cockpit for battle or rest easy as the scenery blurs by? We still enjoy a driver's car over a luxury car--although both are both here. The M5's delinquent demeanor and Adrenalin-junky attitude got into our veins and intoxicated us in a way the more subtle CLS55's didn't. One blast in the CLS55, and you'll feel like you've been there, done that. One sortie in the M5, and you'll want more. The Accidental Comparison
Recently, race drivers Tommy Kendall (representing Mercedes-Benz) and Bill Auberlen (for BMW) demonstrated their car-handling skills to the press at the Motor Press Guild's "Track Days" at Willow Springs Raceway. What were they driving? The CLS55 and M5, of course. Our alert Neil Chirico seized the opportunity to equip each pairing with our Racepak GPS system to record what happened. Below is each driver and car's single best laps presented as a virtual head-to-head comparison.
The visual depiction of results like these is challenging to present. The first graphic below is a perfect example, where speed differences of a few percent become virtually invisible. So to better capture the CLS55 and M5's performance, we've indulged in two, more elaborate presentations; one shows their difference in speed; the third, an illustration of how far the M5 would pull ahead of the CLS55 over the course of one lap.
The three illustrations below are called "curtain graphs"; the base of the curtain demarks the course map, its height represents the magnitude of the result. In the first instance, the height is speed; in the second, it's speed differential; in the third, car-lengths ahead. Obviously, the M5 is quicker--but how and by how much? Read on.
The M5's 2.55-second quicker lap means a big gap on a fast track. The CLS55's brief gains in the transitions and during low-speed cornering logically reflect its better skidpad skills; the M5's gains during braking are likewise consistent with our test-track numbers. What's illuminating are the BMW's cornering and acceleration at high speeds. Our dragstrip measurements from a stop tend to obscure this.
01: Here you see the rise and fall of the cars' speeds over one lap. Did we say "speeds"? The two cars perform so similarly, their plots look like one. Nevertheless, it's fun to note the graph's shape and top speeds.
02: This is a more dramatic visualization. Here we see each car's mph advantage (the difference in their above speeds). Note that the CLS55's few gains seem restricted to the lower-speed transitions.
03: This third depiction really gets to the nitty-gritty. With the two cars starting together on their flying laps, the height of the "curtain" represents how the BMW gradually draws away from the MB.