The SLK55 AMG is the high-performance, range-topping version of Mercedes-Benz' SLK hardtop convertible. The SLK55 is less of a tactile, precision driving instrument than competitors like the Porsche Boxster S, instead providing a combination of brutal power and traditional Mercedes luxury. As with all AMG models, the car sports wider fenders, a lower stance, quad tailpipes, enlarged air intakes, and, of course, a more powerful engine.
The "55" portion of the SLK55's name comes from a potent 5.5-liter V8. Essentially a naturally aspirated version of the engine used in a wide range of other AMG models (there was no room under the hood for twin turbochargers), the powerplant has a 7200-rpm redline and puts out 415 horsepower and 398 lb-ft of torque. Mercedes conservatively states a 4.5 second zero-to-60 miles per hour time, but in reality the sprint takes two or three tenths of a second less.
Transmitting power to the rear wheels is a seven-speed automatic transmission dubbed the AMG SPEEDSHIFT PLUS 7G-TRONIC (brevity is not AMG's strong suit) that utilizes a wet clutch pack in place of a traditional torque converter. The result is gear changes that can occur in just .1 second in the transmission's sportiest shift mode. The transmission features smooth rev-matching during downshifts and has a launch mode for stoplight racing; if drivers want to take control into their own hands, aluminum paddle shifters situated behind the well allow them to do just that.
A cleverly designed sports exhaust system utilizes computer-controlled flaps to allow quiet low-speed operation that won't offend neighbors and a throaty V8 roar when the car is put through its paces. At low engine speeds, the flaps remain closed, keeping the noise level low. Once the driver starts to accelerate more aggressively, the flaps open incrementally: first the to 15 degrees, then 30, and then 50. Upon full throttle, the engine is given free reign to make an eight cylinder symphony.
Helping to balance the SL55's accelerative forces is the AMG high performance braking system. With internally ventilated and perforated brake discs on all wheels, measuring 14.2 by 1.4 inches at the front and 13 by .9 inches. at the rear, the system offers short stopping distances and excellent fade resistance.
The AMG sports suspension is a big part of the SLK55's more playful nature in comparison to lesser SLKs. It includes independent suspension struts with stiffer spring and damper tuning, torque strut bearings on the front axle featuring higher rigidity, stiffer stabilizers at all four corners as well as a more negative camber on the rear axle, all of which conspire to result in high cornering speeds and low body roll in fast S-shaped bends.
When the car is driven through corners in an aggressive manner, the Torque Vectoring Brake system can apply braking power to the inner rear wheel allow the SLK55 to turn precisely and under full control.
A three-stage ESP stability control system allows the driver to select the system's level of intervention at the touch of a button: "ESP ON", with the system fully engaged, "SPORT Handling Mode," which allows a bit of power oversteer, and "ESP OFF" for moments of bravery or foolishness.
The AMG Handling Package, available at extra cost, enhances the SLK55's sporting credentials even further. It is comprised of an AMG Performance suspension with stiffer tuning, an AMG rear axle differential lock, two-piece brake discs at the front and a three-spoke AMG Performance steering wheel finished in premium leather with Alcantara inserts in the grip areas. Unique 18-inch wheels and 174 mph top speed (up from an electronically limited 155 mph) are also included.
Inside, the SLK55 features an interior design reminiscent of the SLS AMG. Specifically calling its big-brother supercar to mind is the car's dash design, with four air vents in the style of jet engines along with a center console finished in brushed aluminum. A steering wheel with flattened top and bottom sections, metal and leather trim and aluminum shift paddles signals the performance-oriented nature of the car, as do numerous AMG badges spread throughout the cabin.
Standard and Optional Features
Befitting the car's price tag, a wide range of luxury and technology items are fitted as standard. These include eight-way power adjustable leather sports seat with heat and memory functions, a 500-watt Harmon/Kardon sound system with a USB/MP3 interface, Bluetooth phone pairing and audio streaming and an AIRSCARF ventilated headrest system that keeps occupants warm during cool-weather top-down motoring.
Two options packages are available. The Multimedia Package brings a COMAND (think iDrive) actived navigation system with voice control and a seven-inch display, Sirius real time traffic and weather info, a 10 GB hard drive for music and an in dash CD changer. The Lighting Package, true to the name, provides bi-xenon headlamps with active curve illumination and a headlamp cleaning system.
Major stand-alone options include a Panoramic roof that renders the entire roof section in glass, automatic dual-zone climate control, a PARKTRONIC parking guidance system and the laser-based DISTRONIC cruise control system.
Mercedes-Benz has long been known for its safety features, and the SLK55 will only add to that reputation. In addition to NECK-PRO crash-activated head restraints, the car boasts eight other supplemental restraints including two-stage front air bags along with dual knee, head and thorax airbags.
Also standard is an 'ATTENTION ASSIST' system that can alert the driver to the first signs of drowsiness, a factor that causes more than 100,000 accidents a year in the U.S.A steering sensor is coupled to smart software that uses 70 parameters to establish a unique driver profile during the first 20 minutes of driving. Between 50 and 112 mph, the system identifies the erratic steering corrections drivers make as they begin to get drowsy and triggers an audible warning and a "Time for a Rest?" message with a coffee cup icon in the instrument cluster.
ABS and ESP are fitted as standard.
The Pre-Safe Brake system is an optional safety feature that senses impending collisions and automatically engages up to 40 percent of braking power and primes the brakes to deliver full power the moment the driver touches them.
Other extra cost-options include a blind spot warning system and a Lane Keeping Assist system, which warns the driver if the roadster begins to drift into an adjacent lane.
Compared to the competitors for the standard SLK-Class, the SLK 55 AMG simply overpowers them - leaving little in terms of competition from a power perspective. But if brute force isn't your thing, the Porsche Boxster S or BMW M3 Convertible may still be worth checking out.