2017 Mercedes-AMG GT Roadster new car review

As far as four-wheel sequels go, the Mercedes-AMG GT Roadster was about as predictable as Batman Returns - it always going to happen.

Yet while the soft-top's arrival was expected, there was anticipation as to whether the new addition to the expanding GT family would add to the AMG hero car or burden it.

After all, the GT is an important car for Mercedes-Benz. A crucial one for AMG, the performance sub-brand that at times accounts for up to one in five sales of the three-pointed star.

That the GT makes up a fraction of those - in two years fewer than 200 have been sold - is irrelevant compared with the halo it glows over the brand.

Which brings us to Arizona, wisping along the multi-lane interstates in the new AMG GT Roadster, a car that ups the artillery against the rival Porsche 911, the icon that AMG has in the crosshairs for its V8-powered, rear-drive hero.

At 120km/h the contrasting fabric roof that accentuates the wide, squat nature of the GT's distinctive long-bonnet shape barely creates a rustle such is the engineering integrity that ensures it closely mimics the comfort and style of the coupe.

The neatly finished trim of the soft-top is in keeping with the detailed metal touches and intricate carbon fibre elsewhere in the two-seat cabin. And, for the trainspotters, a revision to the dash below the quartet of central air vents brings a new recessed piece, something that adds depth to the dash while accentuating the cabin's width.

Push a button and 11 seconds later the fabric roof (available in three colours) is tucked neatly away behind the seats at up to 50km/h.

Roof down and the Roadster sends more air into the cabin, but there's no buffeting and conversations can still continue without raised voices, even while travelling at triple figures.

Now it's up to the spectacular rocky mountains and valleys of Arizona to showcase the driving talents of Mercedes-Benz's most focused and exciting machine.

There are two Roadster models: the regular GT and the newly created GT C, the latter with more power and dynamic nous.

First, though, the regular GT instantly satisfies with its 350kW/630Nm tune of the familiar 4.0-litre twin turbo V8 engine. Despite having less power than the C63 S AMG that is less than half its price, the AMG GT Roadster manages a seamless, grunty thrust that serves as an instant reminder of the scope of an engine that in the E63 AMG makes as much as 450kW.

Sink your right foot and the lengthy snout gently rises as the rear-end squats purposefully.

Aurally subdued in Comfort mode, the exhaust lowers an octave when Sport is dialled up, simultaneously adding much appreciated weight to the light but accurate steering.

Driving through the sleek seven-speed auto it makes for slick upshifts, although it's the whip-like crack on downshifts that delivers on character.

The GT Roadster is also loaded with grip, thanks in part to the broader and stickier Michelin tyre pack that had been fitted to our test car, one that also picks up the light leather interior.

It'll ultimately push the front tyres wide if you carry too much speed into a bend, with the rear is beautifully planted, only fidgeting momentarily with overly ambitious mid-corner throttle applications.

Despite another 55kg of weight due to bracing that compensates for the lack of a roof - AMG claims the Roadster matches the roofed version for rigidity - there's almost no difference in the way the Roadster performs compared with the coupe.

For those wanting extra thrills, the GT C steps it up a notch.

Power and torque jump to 410kW and 680Nm respectively, enough to launch it to 100km/h in 3.7 seconds (0.3 seconds quicker than the regular GT). Fast, then.

The mechanical rear differential is replaced with an electronic one for more precise metering of power between left and right wheels.

It's the start of a substantial dynamic upgrade to the GT C, with four-wheel steering the highlight. The ability of the enormous 305mm-wide 20-inch rear wheels to steer up to 1.5 degrees improves high speed balance, low speed manoeuvrability and overall steering precision.

Below 100km/h the rear wheels turn in the opposite direction of the fronts, effectively sharpening responses by gently tucking the tail in. On the twisty Arizonian mountain passes around the European-like hilltop town of Jerome it seemingly shrinks the aluminium bonded body of the Roadster.

Ramp up the pace and front and rear wheels steer in the same direction, adding high speed stability and subtly but effectively dialling back some of the sensitivity of what is extremely accurate steering.

Helping the traction cause is extra millimetres at the rear. Just like the Porsche 911 the AMG GT is offered in differing widths, with the GT C picking up the wider wheel arches from the track-focused GT R, broadening the tail by 57mm.

It's still possible to overcome the limits of the Continental tyres, but at the same time the immense mid-corner grip of the GT is replicated - even improved slightly - in the GT C, accompanied by the body's impressively flat stance.

The ride is surprisingly supple over generally well presented American roads; It is only on broken edges where the occasional an unpleasant thud will be heard and felt, while coarse bitumen encourages the tyres into a guttural drone.

Potent carbon ceramic brakes arrest the pace superbly, subtly dropping the nose and efficaciously washing off speed.

But the highlight of the GT C is its ability to build on the talents of the coupe. Few cars transition well to a drop-top version, with two-seaters typically top of the tree.

And while compromises are common in convertibles, the GT Roadster has surprisingly few - its price premium is the most obvious. At $284,000 (plus on-road costs) the GT Roadster is $25,000 more than the hard-top version.

The GT C - the coupe version isn't on sale in Australia yet - is $339,000, leaving it a close second to the GT R at the top of the GT tree.

For our money, it's a tempting proposition for a car settling into life within the supercar world. If this is an indication of the sequels Mercedes has in mind the GT has plenty of stories to tell. Bring on more of them...

Don't weight!

Only the bonnet and doors of the Roadster are shared with the coupe in what was a major redesign aimed at maintaining the styling purity and integrity of the hard-top but with the ability to drive roof down.

Mercedes-Benz also created a new material for the bootlid. Combining what it calls SMC (or sheet moulding compound, a plastic) with about 30 percent carbon fibre it makes for a finished piece about half the weight of the steel bootlid used on the coupe.

The non-metallic material also allows for the fitment of the radio's aerials within the bootlid (in the coupe it is in the windscreen).

As for weight, Mercedes-AMG has added extra bracketing to ensure the Roadster body has the same strength as the coupe, which adds 55kg.

The GT's family tree

The addition of the Roadster increases the GT range from five to seven, although only five have so far been confirmed for Australia. Heading things up is the GT coupe and upcoming GT Roadster, each with 350kW from the 4.0-litre V8 that graces all GT road cars.

Then it's into the GT S coupe, with a 375kW tune of the same engine.

The GT C coupe and Roadster (only the Roadster has been confirmed for Australia) get the same basic V8 but with bigger turbos, revised cylinder heads and other tweaks to produce 410kW.

Then it's the GT R leading the performance charge (at least for GTs you can fit a numberplate to) with a 430kW version of the engine used in the GT C.

For those with a race track at their disposal there's the GT3, a track-only version that sticks with the old naturally aspirated 6.2-litre V8 (Mercedes doesn't quote a power figure for the race version).
 
2017 Mercedes-AMG GT Roadster specifications

On sale: June 2017

Price: $284,000, plus on-road costs

Engine: 4.0-litre twin turbo V8 petrol

Power: 350kW at 6000rpm

Torque: 630Nm at 1700-5000rpm

Transmission: 7-speed dual clutch auto, rear-wheel drive

Fuel use: 9.6L/100km (European figure)

2017 Mercedes-AMG GT C specifications

On sale: June 2017

Price: $339,000, plus on-road costs

Engine: 4.0-litre twin turbo V8 petrol

Power: 410kW at 5750-6750rpm

Torque: 680Nm at 1900-5750rpm

Transmission: 7-speed dual clutch auto, rear-wheel drive

Fuel use: 11.4L/100km (European figure)

For more information visit our Mercedes-Benz showroom