2017 Mercedes-AMG GT C Roadster review

Rating: 9.0
$284,000 $339,000 Mrlp
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This is the 2017 Mercedes-AMG GT C Roadster. The big question: Has lopping the roof off AMG's GT halo car robbed it of its monster performance credentials and visceral pleasures? Curt heads to Arizona to find out.
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Forget preconceptions about soft-top options for those who style hair. If you’re shopping for maximum sensor assault with the tri-star badge on the grille, nothing quite tops the 2017 Mercedes-AMG GT C Roadster, the rag-topped twin to Affalterbach's shiniest halo car, the GT R coupe.

But wait, there’s more… if perhaps slightly less. AMG has also released a ‘regular’ 2017 Mercedes-AMG GT Roadster, no ‘C’ attached, lining up with the entry GT coupe, bolstering the flagship super sportcar range to five variants, if you factor in the mid-spec GT S hardtop. Softer, then, if promising a harder experience at a slightly more budget-friendly tier.

Both the GT and GT C Roadsters are due in Oz around September this year. The GT will land with a list price of $284,000, while the GT C will bump the spend up to $339,000. Both prices include GST and any LCT, but exclude the usual on-road costs.

As an introduction to the open-topped delights on offer, we got to blast the pair’s sensory excesses under the blue skies and on scorched earth of the highways and byways in Arizona, Yoo-Ess-Aye.

That the Roadster pair pillage the parallel parts bins of their respective coupes isn’t any great surprise, though there is one crucial reason as to why the king of Benz soft-tops is a ‘C’ and not an ‘R’ designation.

The now familiar 4.0-litre biturbo V8 heartbeat of choice used throughout a number of high-line AMG models gets a 410kW tune in the GT C. That’s 60kW beyond the 350kW GT trim and some 35kW higher than the 375kW GT S, if 20kW short on the humongous 430 figure wrenched from the mighty GT R coupe.

So while the GT C Roadster is well off the leash, it’s not completely so. And perhaps for the sake of that industry buzz phrase ‘model positioning,’ in an effort to maintain the GT R’s status as king of AMG’s lofty performance heap.

Academic differences? While the GT and GT C engines, with their direct fuel injection and ‘hot inside vee’ turbocharger arrangement, are largely identical, the GT produces 350kW at 6000rpm, while the GT C’s 410kW clocks on lower at 5750rpm and holds course until a much higher 6750rpm.

The GT C not only has a larger 680Nm torque swing than the 630Nm GT, with a 1900-5750rpm spread it’s a little broader and higher in the rpm range than the base Roadster’s 1700-5000rpm. Result? The GT C takes the GT’s 4.0sec 0-100km/h time a lobs a hefty 0.3sec off, which is quite some margin this low in the stopwatch stakes, arguably a fair trade for a slight penalty in thirst (a combined cycle 11.4L versus 9.4L per 100 kilometres claimed).

There’s more to that 0.3sec advantage than merely extra outputs. The ‘C’ spec seven-speed dual-clutch transmission gets a taller first and shorter seventh and final drive ratios than the GT’s transmission. Meanwhile, up-shifts are quicker in its exclusive Race mode, an electronically controlled (mechanical) LSD is fitted in lieu of the GT’s passive mechanical unit, there’s wider rear rubber (305mm against 295mm) and active rear axle steering is said to improve high-speed stability through to 316km/h, where the GT is capped at a mere 302.

Other differences? The GT C gets staggered wheel diameters (19s up front, 20s in rear) and also broader front rubber (265mm v 255mm), together with a wider rear wheel track and larger rear bodywork to make it all fit. Result? The GT C shares the same body width as the GT R coupe, some added 57mm in the hips compared with the slimmer GT. Brakes, too, are larger: 390mm front rotors compared with 360mm on lesser variants, though rears are a common 360mm on both rag-tops.

The GT C’s ‘more is more’ approach pays a penalty at the weighbridge, its 1660kg kerb weight some 75kg heavier than GT, though clearly its no anchor to what is superior performance according to the form guide.

While we’re picking details, the GT C also gets a lightweight lithium ion battery, supple nappa leather trim and a bespoke leather/synthetic suede steering wheel, together with a multi-modal so-called ‘performance’ exhaust system…

Both Roadsters get the striking Panamericana grille, with some 15 vertical chromed struts, as debuted on the king of the heap GT R, though the quiet word is the current GT and GT S Coupes will adopt this more striking front fascia as a facelift in future.

Roof up or down, either version is striking in the flesh, though the jewellery-festooned GT C is clear the muscular top dog. Climbing into (or out of) the cabin isn’t a feat enjoyed for the modest, but once inside the seating is suitably low set and there’s a mix of richness and purpose about the interior design. Materials and craftsmanship throughout either variant is first class, let down only fractionally by some plastics, such as the steering wheel trim, and the wheel column stalks lifted from lesser Benzes.

The roof itself is superb. It’s a three-layer design with an acoustic mat insert as sound insulation, draped over a magnesium/steel/aluminium structure. It’s not load bearing – there are integrated rollover bars in the rear bulkhead – but it lifts and stows automatically in 11 seconds at speeds of up to 50km/h.

Thanks to excellent sealing and a large, solid panel that mates to the windscreen surround just above your head, it feels all the part like a solid coupe lid once erected. Once on the move, there’s virtually no wind noise from the structure itself, no booming around the car as you’ll experience in lesser soft-top designs, and the sound isolation properties are, frankly, remarkable.

First, the GT C. At low speed and around town, the Comfort drive mode is downright polite. With the exhaust baffles shut, it can be very quiet, though the deep, bassy thrum of the V8 is ever-present. The dual-clutch gearbox is very slick and near seamless, too, and there’s enough laziness tuned into the driveline in this mode to make low-speed driving a breeze.

There’s a touch of scuttle shake that shimmies the mirror slightly, if only occasionally, at low speed over rough surfaces. Otherwise, structurally, the roadster feels almost hewn from granite. Those impossibly broad Continental Sport Contact 6 tyres do get their roar on at times, despite the rather cool felt-like matting in the inner wheel guard to help suppress noise.

The tyres do slap noticeably over square-edged road joins, which is understandable given their 265/35 front and 305/30 rear profiles. Further, it’s likely that any attempt by AMG to temper the already pleasant ride further via softer joinery in the mostly billet alloy suspension structure, would undoubtedly rob the intimate sense of driver connection to the road the drop-top works hard to celebrate. All that said, the ride and handling balance is very nicely struck indeed.

Pampering comfort, though, isn’t the GT C’s main game. Instead, drop the roof, hit Sport and open up the adaptive exhaust’s lungs and out comes that sensory overload that’s crucial to the experience as promised.

The top-spec version offers a further Sport+ and a manic Race mode not available in the GT, as well as driver assignable Individual. And what AMG is really getting right of late is achieving tangible leaps in character – noise, urgency, drama – moving up through the modes.

Sport flexes the GT C’s muscles markedly, though only enough to provide real purpose around town, on the open road or on the highway. There’s nothing manic about it, but dig in and the two-seater will happily eat straights or curves with a healthy appetite. And yet it never drops the refinement ball while doing so, the powertrain remains assertive without ever becoming manic or too highly strung.

I put about 150 kilometres of balanced normal driving under the GT C’s wheels heading north out of Phoenix towards the mountains surrounding the town of Prescott, home to some of the best twisty roads in this neck of the West Coast woods. The kinds of roads you need to uncork the properly heroic Sport+ mode.

The first rise is a succession of constant radius double-lane sweepers and here the GT C sits impossibly flat and planted, generating impossible grip while tracking like it's on rails. It’ll whip up a heady pace even at part throttle and neither end of the car will budge off a chosen line by as much as a millimetre. And despite its fairly wieldy size – it takes up a lot of real estate between the lane markings – the excellent, direct steering makes safe and accurate passage child’s play.

What gushes from the GT C is utter purpose. And whether it’s the active diff or steering, or perhaps its calibrations and tuning, it feels more tied down and on a mission than I remember the GT S Coupe to be. It’s less darty on the nose, not as loose in the tail, perhaps more confidence inspiring at a red-hot road speed if less edgy and, arguably, not quite as thrilling. But for A-to-B transit, it’ll make as much haste as you ask it to.

The last 10 or so kilometres before hitting Prescott, the road narrows and tighten up, which gave the optional 402mm/360mm carbon-ceramic brakes a thorough workout, though the power or accuracy on tap is impressive and they barely break a sweat. On hot mix, the GT C is a slot car, but it takes a surface change, to some slipperier brown stone material, to find some natural and safe understeer.

It's its rear end, though, that’s remarkable. On road, at least, it's tough to make it budge. It takes the broken road or corner exit bump for the tail to shift even slightly, and it does so predictably and with just a faint flicker of the traction control light in the dash, even with the throttle pinned hard into the floor. This level of ability is perhaps why you’d fork out the extra for the GT C version. And that’s before you get the rag-top off street, on track and activate its ultimate Race mode, which loosens the safety reins considerably and, frankly, too anti-socially for road. Or so I’m told…

I’m also told the GT C Roadster isn’t quite as visceral as the GT R coupe. Perhaps not. But the flagship drop-top is clearly cut from similar cloth that imparts a purpose and focus that mightn’t be categorically ‘supercar’ but comes bloody well close for what is, essentially, a super sportscar that’s drunk red cordial.

I swap into the lesser GT Roadster and retract The Good Roads for back-to-back comparison. And I came away from the experience liking the ‘base’ car a little more, much to own surprise.

Creeping out of Prescott in Comfort, the GT is nigh on identical for tractability, general comfort and pleasantness. There’s no dilution in vibe or mojo, feels equally the sportcar on steroids even at a cruise, such is the toey nature of the engine, the refinement of the gearbox and the sense that it’s ready for action stations at a plunge of the right foot.

Sport+ activated and diving into the corners, its slightly narrower 255/35 front Michelin Pilot Super Sport tyres seem to provide slightly more accuracy and bite on turn-in – strange but true. But the big difference is the GT, with its passive mechanical differential, no rear-axle steering trickery and 295/30 rears (on optional 20-inch rear rims), is a little looser.

It’s a give and take situation. On one hand, it doesn’t drive as hard out of corners with unflappable GT C-like traction. But on the other, it's more playful, and therefore fractionally more fun, moving the tail around a little to point the car form one apex to another. For my tastes, I’ll trade the former – and perhaps some outright pace – for more of the latter.

Surprisingly, the GT’s biturbo V8 doesn’t feel 60kW down in top-end energy or 50Nm short in corner exiting shove. It’s also got a slightly different engine note, specifically more bark if a little less volume, perhaps due to the non-adaptive exhaust system. No complaints from the relatively modest 360mm steel brakes either – if anything, they’re a little more progressive in feel and allow more accuracy at a brisk on-road pace.

By being a little less focused on A-to-B expediency, the GT is actually a little sweeter to drive. And when the difference in outright pace, on road at least, is quite negligible, it’s the GT that’s making a slightly more compelling argument. At least, that is, for this scribe’s personal tastes.

Downsides? On the move, both cars can be caught snoozing a little to kick down for those sudden overtaking opportunities. And by nature of the cabin layout, nearly all of the centre controls, including the infotainment system, are awkward to access because of their close proximity to the driver. You almost need to reach over with the wrong hand to use the dinky little transmission selector.

But what might be deal breaker for some buyers is the GT Roadster focuses so much on going forward, it’s a pain going backwards. The low-slung seating, the small rear window, the broad rear hips: it’s a right pain to reverse park either variant, and that’s despite a very large rear-view camera view on screen.

Impressive? You bet. Our advice is to not part lease payments for the coupe without sampling a roadster first. Further, don't stump up for the GT C without having a good hard look at the GT first. Having said that, the high-spec version does get enough extra goodies, outputs and tech to warrant the $55,000 premium.

Watch for this pair to hit Oz late in the third quarter this year. Here’s hoping there’s a racetrack available on which to fully uncork the GT C locally.

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