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The SLK55 is a Mercedes-Benz, so you expect it to be a refined automobile with luxurious amenities.

It's also an AMG, so you know it's fast. However, fast is a relative term.

The previous-generation SLK was "fast". The SLK32 had a supercharged and intercooled 3.2-liter V-6 that produced 349 horsepower and 322 pound-feet of torque. It weighed 3200+ pounds, could reach 60 mph in 4.8 seconds, and crossed the quarter-mile in 13.0 seconds at 110 mph. The new model, the SLK55, has a 5.5 liter, 24-valve, naturally aspirated V-8 that makes a mere six additional horsepower. It has an additional 54 foot pounds of torque, but it also weighs an additional 190 pounds, so how fast can it be?

How about "Corvette fast"?

Yes, that Corvette; The 400 horsepower C6. Since were discussing performance, the six-speed model. In addition to a power advantage of 45 horsepower and 24 foot-pounds of torque, the Corvette roadster weighs 155 pounds less than the SLK55. In spite of these advantages, the Corvette roadster and the SLK both take 4.3 seconds to go from zero to sixty. In a quarter mile, the SLK55 is faster. The SLK55 runs a 12.7 in the quarter, while the Corvette runs a 12.8. Just so that we're perfectly clear about the cars and conditions, in 2005, both cars were tested by professional drivers and Car & Driver magazine published the results. The Corvette was the six-speed model, had the Z51 performance package (that included larger brake rotors, lower gear ratios, firmer suspension, and Goodyear Eagle F1 Supercar tires), power top, a DVD nav system, OnStar, and the preferred equipment group. That particular Corvette roadster listed for $62,080. The SLK55 was a standard model - not a Black Series. The only options were metallic paint and Airscarf neck heaters. That SLK55 listed for $63,550. Both cars were driven with the tops up.

Hard to believe? Consider this: The SLK55 is as fast as a W211 E55 from zero to sixty mph, and is just two tenths of a second slower in the quarter mile. The E55 has a 469 horsepower supercharged V8. Hopefully we're now all in agreement that the the SLK55 is fast.

How is this possible? Gearing. Until the SLK55, all M113 AMG vehicles used a 722.6 five-speed automatic. The SLK55 comes with an AMG Speedshift equipped seven-speed. This transmission, the 7G-TRONIC, has been specifically tuned by AMG and shifts 35% faster. It comes with aluminum shift paddles on the steering wheel, but I think it works best when left in drive. When allowed to shift on it's own, the engine never falls out of it's powerband. The toughest part is the launch. To get the car moving, the driver has to modulate the throttle so as not to induce wheel spin. Once moving, the driver can simply floor the accelerator and hold on. The engine revs will climb to 6700 RPM, drop down to 5000 RPM after shifting, and begin climbing again. In the SLK55, acceleration isn't peaky. It's a constant pull with slight interruptions while the transmission shifts.

It's not all about acceleration. A fast car needs good brakes. From 70 MPH, the SLK55 brakes stop in 156 feet. In comparison, that same Corvette roadster with the Z51 package's bigger brakes and Eagle F1 Supercar tires, takes 170 feet from the same speed. The goal here is not to disparage the Corvette, but to recognize it as a seriously fast car that makes a very good performance yardstick.

Of course, it's not all about performance either. Mercedes-Benz vehicles are known for safety, and the SLK55 is no different. With the retractable hardtop down, in the event of a rollover the occupant's heads are protected by dual micro-alloy steel roll bars and oval steel tubes in the A-pillars. The car's six airbags include dual knee airbags, and head/thorax side-impact airbags. The seat belts feature Emergency Tensioning Devices (ETDs), and adaptive belt-force limiters. If an airbag deploys, Tele Aid can automatically call for help in the event the occupants cannot.

Despite the safety features, I'd be quite hesistant about loaning an SLK55 to teenagers. The engineers at Mercedes-Benz did their best, but the laws of testosterone and physics still apply.

Technical Data

© 2010 Marcus Blair Fitzhugh

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