Mercedes-Benz SLK 55 AMG 2008 Review

What we liked
>> Airscarf -- every drop-top should have one
>> SLK 55's uncompromising nature
>> SLK 350's more moderate manners

Not so much
>> Slow paddle-shift response
>> 'Thoughtful' throttle
>> Luggage space as stingy as expected

Overall rating: 3.0/5.0
Engine/Drivetrain/Chassis: 3.0/5.0
Price, Packaging and Practicality: 3.0/5.0
Safety: 3.5/5.0
Behind the wheel: 3.5/5.0
X-factor: 3.5/5.0

About our ratings

OVERVIEW
When Mercedes-Benz introduced the original R170 generation of SLK, it was very much the retro sportscar. Porsche's Boxster had been in the SLK's sights, but while the Boxster is the car that saved Porsche, the SLK has been a relative 'also-ran'.

Enter the R171 model (more here), which forsook the retro look for a clever style that has capitalised on MB's modern F1 involvement.

Now, the R171 has been upgraded, with more equipment, some cosmetic changes and worthwhile improvements for the 1.8-litre supercharged four-cylinder Kompressor engine and the 3.5-litre V6.

PRICE AND EQUIPMENT
The upgraded SLK model range is priced from $86,780 for the SLK 200 Kompressor, rising to $112,380 for the SLK 350 and topping out at $164,900 for the SLK 55 AMG.

Both the four-cylinder and V6 models are offered as six-speed manuals. In reality only a handful of manuals will be sold. They are available with an automatic transmission option -- for an additional $3120 in the case of the SLK 200 Kompressor's five-speed ($89,900 inclusive) or $3520 for the SLK 350 with the seven-speed unit ($115,900 in total). The SLK 55 AMG is now fitted as standard with the 7G-Tronic box offered as an option for the SLK 350.

As part of the 2008 upgrade, the entry-level SLK 200 Kompressor gains a new multi-function steering wheel, leather bound and in a three-spoke design. Remote controls on the steering wheel operate the six-disc CD changer audio system, which is MP3-compatible and outputs information to the 5-inch colour monitor in the centre fascia.

Another display, in the instrument binnacle, provides information from the trip computer, as well as the audio system, phone (and optional satellite navigation).

Dual-zone climate control complements the leather-trimmed heated seats, which are, at this level, manually adjustable -- as is the steering column rake and reach.

Safety features as standard include the rain-sensing wipers, auto-on/off headlights, ABS/ESP, Brake Assist, dual front airbags and side-impact airbags.

Over the SLK 200's specification, the SLK 350 offers the Comand APS information and entertainment control system, which incorporates a DVD-based satellite navigation system and a larger (6.5-inch) colour information monitor. In addition, Airscarf, a HVAC outlet from the seats to warm the back of the neck for driver and passenger, is a standard feature. Both Airscarf and the Comand APS features can be specified as options for the SLK 200.

Seats and steering column are all electrically-adjustable in the SLK 350.

The SLK 55 features a 5.4-litre V8, 7G-Tronic automatic and an AMG-developed high-performance braking system with cross-drilled ventilated discs and silver calipers at the front. Ditching the 17-inch alloy wheels of the lesser variants, the SLK 55 AMG gets around on 18-inch wheels guided by an AMG-tuned version of the Direct-Steer system.

Inside, the V8 variant is specified with paddle shifters for the automatic transmission, sports seats, a Harman/Kardon audio system, electro-chromatic mirrors (including the electric-fold-in exterior mirrors) and an alarm.

MECHANICAL
All three engines are mounted longitudinally and drive to the rear wheels. The supercharged four-cylinder in the SLK 200 Kompressor is a DOHC unit of undersquare dimensions (82.0 x 85.0mm bore and stroke). Peak power is 135kW at 5500rpm and 250Nm of torque is available between 2800 and 5000rpm. That's an improvement of the previous generation of 15kW and 10Nm, respectively.

Combined-cycle fuel consumption is 8.0L/100km for the manual variant, which emits 190g/km of CO2. The auto delivers 8.2L/100km for the same cycle.

The V6 in the SLK 350 has been upgraded significantly and now revs harder (it's dubbed Sportsmotor internally at Benz), with a maximum engine speed of 7200rpm attainable for short periods. Peak power is up 24kW to 224kW at 6500rpm and peak torque has been increased by 10Nm for a new figure of 360Nm at 4900rpm. Those improved figures result from a higher compression ratio, a new intake manifold and a revised valvetrain.

Driving through the six-speed manual transmission, the SLK 350 uses 9.5L/100km of fuel and produces 227g/km of CO2. The auto is 0.3L/100km more frugal.

In addition to the performance mods, the V6 has been revised for an improved exhaust note on the overrun and, mated to the 7G-Tronic seven-speed automatic transmission, throttle blips during downshifts in sport mode to match engine revs to road speed.

Mercedes-Benz left the SLK 55 powerplant untouched for the upgraded model. The naturally aspirated engine produces 265kW and 510Nm.

The six-speed manual transmission fitted as standard to the four-cylinder and V6 models features an overdrive sixth gear and a direct-drive fifth. Only the SLK 200 Kompressor is offered with the option of a five-speed automatic, the V6 and V8 models both benefiting from the seven-speed 7G-Tronic automatic transmission, as an option for the SLK 350 and as standard for the SLK 55 AMG.

Drive reaches the rear wheels through a multi-link IRS system, which is balanced at the other end by MacPherson struts. The variable-ratio rack-and-pinion steering is power-assisted and, in the case of the SLK 55 AMG, provides variable assistance according to the road speed.

Alloy wheels measure 7.5J x 17 at the front and 8.5J x 17 at the rear for both the SLK 200 Kompressor and SLK 350. These wheels are fitted with 225/45 R17 (front) and 245/40 R17 (rear) tyres.

With its higher performance potential, the SLK 55 AMG comes with wheels and tyres measuring 7.5J x 18, 225/40 R18 (front) and 8.5J x 18, 245/35 R18 (rear). For all three variants, the brakes are ventilated and cross-drilled at the front, but solid at the rear.

Kerb weights range from 1390kg for the SLK 200 Kompressor, with six-speed manual, to 1575kg for the SLK 55 AMG.

PACKAGING
It goes without saying that a small, two-seat convertible sportscar that must 'swallow' its own roof is not going to be accommodating when it comes to luggage, kids, pets, big people, spare tyres... yada, yada, yada. It would be nice to tell you that the SLK surprised with its voluminous interior room and deceptively spacious boot -- but it didn't.

In the boot, there is just enough room for a couple of small cases with the roof open, so any long journeys are best undertaken with the roof raised. Even with the roof up, owners will struggle to accommodate anything especially large and/or bulky, although Mercedes-Benz has developed storage pockets within the boot and an audio/visual alarm will alert the driver to an obstruction in the boot preventing the roof folding down.

Also to the SLK's credit, it's a comfortable car for the two occupants and, unlike some convertibles in the past, there's no need to contort the body and tilt the head on an angle to peer beneath the upper frame of the windscreen.

Not so much to its credit, the SLK is a bugger of a thing to leave, between the low-riding stance and the deep seats. Most women drivers will feel more at ease if they wear slacks while driving the SLK.

Even males will find themselves quickly adopting the bespoke film hero pose exiting the car. That is, place the outboard hand on the door sill and push down as you vault out through the door. Holy fingerprints on the scuff plates, Batman!

Once seated in the SLK, there's plenty of head and legroom, with highly flexible adjustment for seating, steering tilt and reach. The seat has to be lowered quite close to the floor for an unobstructed view of the instruments. Switchgear placement is sometimes compromised by the compact packaging in the SLK -- the headlight switch is not that easily reached, below and to the right of the steering wheel.

Cupholders were located in the upper section of the centre fascia, rather than in the centre console; where it might block use of the handbrake. On balance, that's a good thing, but further highlights the constraints placed on the car's designers by the need to package features efficiently in such a small car.

The SLK's trademark folding hardtop provides an extra level of amenity and security over soft-top convertibles, especially if (like many these days) you're not blessed with off-street parking.

SAFETY
Mercedes-Benz has equipped all three variants of the SLK with pop-up roll-over bars behind the seats -- a facility pioneered in the old R129 generation of Mercedes SL from the early 90s. This feature, combined with dual front airbags, side-impact airbags and seatbelt pre-tensioners ensures that the SLK is well endowed with an appropriate complement of passive safety appointments.

On the active safety front, the SLK, even at entry level (SLK 200 Kompressor), is fitted with antilock brakes, stability control and Brake Assist. Rain-sensing wipers, auto-on/off headlights and foglights at the front and rear are also part of the specification, carrying right across the range.

This will be covered in the ON THE ROAD section below, but every variant of the SLK impresses with the size of tyre contact patch, relative to its performance potential and weight. Being properly tyred and with the correctly tuned dynamic safety systems, it's a car that won't fall off the road without some serious prompting.

COMPETITORS
If you subscribe to the view that only rear-wheel-drive sportscars should be compared with the SLK, you'll consider the BMW Z4 and the Porsche Boxster, but virtually nothing else. Nissan's 350Z is a cheaper alternative but won't carry the cache of the Benz badge.

You might also consider the Alfa Romeo Spider V6 and the Audi TT Roadster 3.2 quattro. There are also four-cylinder variants of these cars that might be an alternative to the SLK 200 Kompressor at a pinch.

ON THE ROAD
The drive program for the SLK got off to a slow start with a truck breakdown blocking traffic on a major freeway out of Brisbane for the best part of an hour. It was not an ideal start, but we did get to enjoy the SLK with top-down -- even if it wasn't quite in its natural element: surrounded by diesel fumes, with truckies shouting traffic updates to each other.

The brisk SEQ winter breeze was dispelled by the Airscarf feature, which was worth its weight in gold.

On the move once more, it became apparent that the SLK 55 was fast but the power delivery was 'soft'. The engine needed to be revving hard and it felt like the ECU wouldn't deliver full torque immediately on demand. This could be a safety aspect of the design or it could be a tactic to protect the driveline from abuse.

The V8 engine is a fairly peaky unit that was fitting for a sportscar, but needed a fairly good, hard prod of the right pedal for best results. It wasn't the sort of engine to thrive on part throttle.

The SLK 200K was also inclined to rev, needing more engine speed to deliver torque than one would expect from a supercharged engine. There was a very distinct whine once the engine was working harder, but the exhaust note lacked the ultimate excitement of the V8 in the SLK 55 AMG -- one of the most charismatic engine notes of any V8 sampled in recent times.

In some ways, the SLK 350 was the ideal balance. It had a little more punch than the Kompressor model and would rev as readily as the other two engines -- if not more so -- and it offered better midrange torque than the supercharged engine.

Shorter in length than either the Kompressor engine or the AMG V8, the V6 probably contributed to a slightly better weight distribution in the SLK 350. This manifested itself in its better handling and steering across a range of roads.

The SLK 200 Kompressor was a bit lighter on its feet than the V8 sibling, despite being fitted with slightly firmer sports suspension. The ride in the supercharged four was substantially better than the SLK 55's and, with its greater compliance, was less likely to be knocked off line. Lay some blame also at the 55's lower-profile tyres which exacerbated the unsympathetic ride.

All models provided good steering feedback, but the added weight in the nose of the V8 made for less consistent steering, which needed more adjustment through a typical corner than either the four or the six did.

All three were close to neutral in handling (although not as close as big brother SL, as we discovered the day after driving the SLKs) but the SLK 55 is slightly more like a go-kart than a sophisticated sportscar. With its magnificent engine and tied-down suspension, it would be fantastic for track days, but subjectively, a touch too uncompromising during the week.

Our Kompressor testcar was a manual and the gear shift was light and easy to use. It's not a particularly short throw selection, but that's what makes it easy to live with.

In both the SLK 350 and 55, the paddle-shift feature was slow to respond at times and tended to be overridden quite readily by kickdown, or from the adaptive shift programming. We were informed by Benz that without the driver selecting Manual mode first, the sequential-shift would take a back-seat to some indicator that emergency acceleration was required (the kick-down, specifically).

Kick-down in the SLK 350 was, when used as drivers will in an emergency, too ready to select the lowest possible gear.

On one or two occasions, the transmission would kick-down to third, running the engine up close to its maximum speed without anything left in reserve for on-road acceleration. You don't want that lower gear from kick-down if the box is only going to hold it for the last 500 revs before changing up to the higher gear you wanted in the first place.

The SLK 55's brakes were impressive for their performance, but the pads were plainly high in metallic content and those brakes were arguably more at home on the racetrack -- much like the rest of the car.

All three variants provided a generally comfortable driving position, with the seats in the 55 taking top spot for all-round comfort and support. Instruments and controls were simple to use and easily accessible, for the most part. The cruise control and the lane-change facility for the indicators were particularly welcome features.

NVH was commendably low, even with the top down and there was no detectable scuttle shake. The wind deflector and raised side windows made a major contribution to keeping the occupants warm, but it was the Airscarf system that earned its dues as the best thing since sliced bread in this open-top car -- toasty-warm sliced bread, to be precise.

Everything considered then, there's not much reason to pick fault with the SLK. It's quite different in nature from one variant to the next.

Many buyers would be happy with the SLK 200K as a 'budget' alternative, whilst others would love the in-your-face attitude of the SLK 55 AMG. For this Goldilocks, however, the SLK 350 is just right.

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