Review: Mercedes-AMG GT Roadster

Detroit muscle cars bask as the sun's ultra violets tear their dashboards to shreds. Outside the yard, I've parked a car not so very different in style even though they are separated by almost sixty years. Mercedes-Benz's AMG GT Roadster is the tuning division's third go at a whole car after the 2010 SLS and the 2015 GT coupé. AMG will tell you it's a Porsche 911 competitor, but at heart, the GT Roadster is an old-school muscle car.

It's also damn good looking. That convex radiator grille is called 'Panamericana' after the eponymous race, which was won by Mercedes in 1952. The long bonnet has more ducts than an air conditioning unit, with coachwork swages that run into each other with purpose and menace. Not quite so sure about the rear, which is often a weakness in soft-top versions of coupés, and the small rear spoiler mounted behind the sheet-moulded-plastic and carbon fibre boot lid looks a bit ridiculous as it whirrs up and down at speed.

Two versions of the Roadster will go on sale this summer; the 470bhp £110,145 standard GT (£11,400 more than the equivalent coupé model), or the 550bhp £139,445 GT C Roadster, which has a wider body to accommodate its larger wheels, tyres and wider track, an electronic limited-slip differential and electronically adjustable dampers. We are also expecting a GT S roadster (as well as a GT C coupé), though there's unlikely to be a drophead version of the R coupé.

The underbody is all aluminium and magnesium; a space frame with extrusions welded into castings for featherlight strength. Not so very feather light, though, since with a driver on board, the GT C tips the scales at 1.7 tonnes. The suspension is upper and lower wishbones all round and the driveline is old-school hard charger, with the dry-sump, biturbo four-litre V8 feeding drive into carbon-fibre propshaft braced with a torque tube and into a seven-speed automatic transaxle, with AMG's mechanical clutch in place of a torque converter. 

That V8’s a thing of beauty. Loosely based on two four-cylinder A45 units, it has normal V8 breathing reversed so the twin elephantine turbos lurk within the vee, fed via serpentine trunking with fresh air and exhaust gas out of the inward facing ports. The inlet ports are on the outside of the cylinder heads so the pressurised air is delivered around the front of the block via a brace of water-to-air intercoolers and the exhaust gas goes straight off the back of the block and into the exhaust pipes. Nice...

With tall sills, clambering into the cabin isn't the work of the moment, and once ensconced, the firm seats feel snug and a bit unforgiving. There's not much spare room in there, with a massive transmission tunnel, tiny door pockets, a ridiculously small glove box and shallow centre console. Fortunately, the 165-litre boot is large enough for a pair of squashy bags.

With a twin-dial instrument binnacle and twin rows of piano-key switches, this is a classic sports-car facia. There are big rotary switches down the centre console to operate the driveline options and Mercedes's rotary capstan control for the audio and sat-nav screen mounted high in the centre of the dash. It's all pretty much contiguous with the driver and sort-of comfortable, but with no space behind the seats, you have to be organised for long journeys.

There are 11 coachwork colours (Solar Beam yellow costs an extra £7,500!), three hood shades and 10 interior trim textures. Best, in our opinion is the satin gunmetal grey (Designo Selenite at £2,145), with a sail-cloth red hood and darkish leather with piano black highlights.

As you might expect, performance is suitably barnstorming. The standard Roadster will rancorously sprint from 0-62mph in four seconds with a top speed of 188mph, Combined fuel consumption of 29.4mpg and CO2 emissions of 224g/km. Equivalent figures for the C version are: 3.7seconds, 196mph, 24.7mpg and 259g/km.

Start up either version and the V8 throbs the air, bellowing defiance at the politically correct and dubiously ecological. Its width, crackling power and look-at-me appearance makes this a bombastic motor car; all latent power and portent. Out on the wide interstates of Arizona, the engine felt unburstably stentorian and unstoppably strong. With a speed limit of 65mph, it was all we could do to stay legal. And when the going got wet and snowy in the mountains to the North of the state, we found the traction control to be just as brutal. Experience tells us the handling is more benign than it at first seems, but with all that power, you need to take great care on anything other than race-track smooth and bone-dry surfaces...

As well as its rear suspension from the SLS, the GT Roadster we drove had 265/35/19 Continental front tyres, 305/30/20 rears, with £1,795's worth of AMG Dynamic Plus package comprising dynamic engine and transmission mountings, firmer, specially-tuned suspension and a Race mode for the transmission and dampers. It also comes with the GT R coupé's rear-steering system, which turns the rear wheels by up to 1.5 degrees, in the same direction as the fronts at high speed to make the car feel more stable, and against the fronts at low speeds to make it more manoeuvrable. Further wallet-depleting options were £5,995 carbo-ceramic brakes and £1,495 adjustable damping.

All that suspension stiffness is immediately apparent in the C, which is unpleasantly harsh over bumps. Anything like a typical British sharp-edged pothole issued loud reports from the tyres and a jolting snap to the body. In the UK, this isn't going to be comfortable.

The electronically-assisted variable-ratio steering feels well weighted and accurate, but over geared and slightly darty. Moreover, it lacks much in the way of feedback and there's a small dead period around the dead-ahead position. In spite of the humongous grip generated by the super-wide tyres, it didn't feel that confidence inspiring to drive fast and actually a bit twitchy at high speeds.

By contrast, the standard car with its narrower Michelin Sport Pilot tyres, softer suspension (especially at the rear), more fluent steering and better-mannered power delivery felt more comfortable and wieldy. The suspension 'breathed' better on Phoenix's more uneven roads, and there was less noise and reaction to expansion joints and over-banded road repairs.

The GT Roadster will remain a rare sight on UK roads; sales of the coupé have been no more than a couple of hundred a year and limited supplies will ensure the Roadster will be just as scarce. For some buyers, the draw of the all-the-bells-and-whistles C version will prove irresistible. Fact is, however, outside of a race track, the standard £110,000 Roadster is a better drive, a more rounded car and actually more fun.