Mercedes-Benz S55 AMG

Mercedes-Benz S55 AMG Mercedes-Benz S55 AMG
Short Take Road Test

That's right. Although BMW's high-performance M cars regularly upstage their opposite numbers at Mercedes-Benz's in-house tuning shop, AMG, in this one application the Benz boys hold the aces. The Mercedes S55 AMG will just flat dust anything from the BMW 7-series portfolio, in part because that's the one model for which no M variant — M for Motorsport — exists. BMW's corporate reasoning seems to be that the folks who go about their high-end business in high-end rides such as this one aren't interested in boyish stuff like increased roll stiffness, enhanced grip, and more thrust.

Mercedes figured — correctly — that these interests do not necessarily evaporate as a result of advanced socioeconomic station or the accumulation of years. The Benz crew also figured this was a chance to one-up its hot-rod rivals from BMW. Which is what the S55 AMG is all about.

On the other hand, BMW does offer a Sport package for the 7-series that includes more aggressive tires, stiffer suspension tuning, and on the 740i, a lower final drive to enhance getaway. The last 7-series sedan to pass our way, a 740iL ("The Dowsters," November 1999), lacked the lower final drive and required 7.2 seconds to reach 60 mph, 18.5 to reach 100, and 15.6 to cover the quarter-mile, touching 92 mph at the lights. The S55 hit these same marks in 5.5 seconds, 13.4, and 14.0 at 102 mph — very brisk by any standard but particularly impressive for a Teutonic executive express that weighs in at 4260 pounds.

Even at that elevated avoirdupois, the S55 is 54 pounds lighter than its BMW rival, but that's not the prime element in its lively response to the spur. The AMG edition gets there quicker thanks to more motor — 354 horsepower and 391 pound-feet of torque from the same 5.4-liter SOHC 24-valve aluminum V-8 used in the E55, ML55, CL55, and CLK55. That's 52 more horsepower and 52 more pound-feet than the 5.0-liter V-8 that propels the S500, and it adds up to acceleration advantages across the board. (The lordly S600, with its 362-hp, 5.8-liter V-12, is actually a hair quicker, but not quite as nimble on its feet.)

Which brings us to the agility issue. As is true of the other AMG massages, there's more to the S55 than enhanced muscle. Specifically, there's more tire-contact patch and less sidewall to flex. The S55 wears no-nonsense rubber — 245/45ZR up front, 275/40ZR at the rear — on 18-inch aluminum alloy rims, more meat than on any of its stablemates, which translates as short stopping distances and lots of cornering grip. Our S55 tester turned in an impressive series of 70-to-0 stops within a couple feet of 163 and recorded 0.90 g on the skidpad, an outstanding level of grip that's in top-rank sports-car territory.

This car also has a secret weapon — active body control (ABC) — that sets it apart from all BMWs, M badges or no M badges. A quartet of computer-controlled hydraulic servos rides atop each coil spring. When the system's 13 sensors detect and interpret body motions — dive, squat, roll — the servos effectively increase appropriate spring rates to keep the car level. ABC operates full time and includes a "sport" setting that reduces body roll by as much as 95 percent (68 percent in the normal setting).

Replacing conventional anti-roll bars, ABC performs essentially as advertised, but its response time isn't quite as quick as Mercedes would like to believe. Even though the system is capable of updating every 10 milliseconds, there's still a small but discernible lag in the car's responses during slam-bang transitions, such as the fast uphill turns leading to the Watkins Glen back straight, or the downhill esses at Road Atlanta. We got acquainted with this odd phenomenon — variable roll stiffness in midcorner — during the recent One Lap of America run ( C/D, August 2001), and we're not convinced it's as effective as a more conventional handling package, with stiffer springs and firmer shock damping — particularly in view of the S55's slightly stiff-in-the-knees ride quality.

On the other hand, even though this is perhaps the least aggressive of the AMG packages, the S55 delivers a level of performance that's unique in the realm of luxury sedans. As is often the case, we wish it weighed a little less; all that mass inevitably retards cornering speeds and transient responses. It wouldn't hurt if it cost less than $101,071 to start, either. But for covering long hauls in short order — and in high style — it just doesn't get much better than this.