Just occasionally a convertible comes along that proves better to drive than the coupé upon which it is based. In theory, and all other things being equal, this should not be possible. Unless built on a ladder-frame chassis like a Land Rover Defender, an open car will always be less structurally sound than its closed sister. As a result its suspension will work less well which, were the manufacturer responsible not prepared to make extensive modifications to the car to mitigate this effect, would be fairly disastrous. But even with substantial additional cross bracing under the car, I have yet to hear of a convertible that is as stiff as the equivalent coupé or one which, because of said strengthening, is not also heavier too. Which means it will be slower, have poorer handling, a worse ride and compromised steering. Almost always.
In the recent past I can think of just two that have defied these odds, and indeed physics, and been better to drive without a roof. The first was Alfa Romeo’s 8C, the second the Bentley Continental GTC. But they are exceptions because they were developed after their closed cousins, giving their engineers further time to hone the chassis and suspension. Truth is, these cars were better to drive not because they were convertibles, but despite it.
But if you read and believe the motoring press, a third is among us, and this is it: the Mercedes-Benz SLS AMG Roadster. Unable to attend its formal launch I sat back in wonder at tales of how this open sports car actually improved on the standards of the SLS coupé despite, crucially, being developed at exactly the same time and therefore denied the advantage enjoyed by the aforementioned Alfa and Bentley.
The numbers are actually very impressive. Most importantly it weighs just 40kg more than the SLS coupé, though it should be said that this is in part due to the mass of the discarded gullwing doors. Nevertheless, with 563bhp to play with, adding the weight of a small child was never going to make much difference – so little in fact that Mercedes has felt no need to modify either its claimed acceleration or top speed.
But I was keen to see for myself. For as long as I can remember I’ve considered that where recreational motoring is concerned, fast cars should be closed and slow ones open. If you’re going to be travelling quickly you don’t want to be disturbed by the wind whipping your face, nor your vision blurred by scuttle shake induced by a lack of structural integrity.
At first, those who advocate the Roadster’s superiority over the coupé appear to have a point. As you might expect Mercedes has done more than merely slice the roof off the SLS, and in addition to the strengthening that has taken place, so some softening has occurred too. Its spring rates have been reduced, the dampers slackened off a touch. At the front the steering geometry has been modified, at the back some passive rear steer introduced. And for a convertible with an inevitably less hardcore brief, these changes make great sense. You notice particularly the ride quality, which has improved from merely mediocre to perfectly passable.
If all you’re going to do is waft around, why not do so with the roof down? It’s a task it can perform in scarcely more than 10 seconds and so long as you’re within the urban speed limit you don’t even need to slow down. The roof stows almost flush behind you, though leaving some untidy holes in the rear deck. It’s probably prettier than the coupé, but far less imposing.
Two things strike you. First is that however good the 563bhp V8 sounds in the coupé, it’s better by far in the Roadster. At low revs its timbre is not unlike a race-prepped small block Chevrolet motor, but as the needle races around the gauge, the cultured howl above 6000rpm reveals a rare class. As noises to quicken the pulse go, you’d need a V12, probably emanating from the Maranello region of Italy, to beat it.
Less obvious but no less impressive is the wind management. Mercedes has thought hard about how SLS Roadsters will tackle the challenge presented by La Croisette and the Promenade des Anglais as they burble between Cannes and Nice, and have directed the airflow everywhere but over you. But even on a Welsh mountain in November its aerodynamic effectiveness combined with roasting seat warmers, a splendid heater and Mercedes’ unique ‘air scarf’ hot air blowers in the seats means it would be a shame and a waste to regard this car as a summer’s day recreation.
And yet. Given a straight choice between the two, I’d not consider the one with the folding roof. It’s not the money – indeed at this level I consider the £8500 mark-up on the Roadster rather restrained – but the sense of occasion that would keep me in the coupé. Partly it’s the looks: heresy though it is, I think those gullwing doors look even better on the SLS than they did on the 300SL and if I chose the Roadster I would miss them. Plus I have no need to be seen in this or any car, so the top-down, look-at-me appeal is rather lost on me.
What I can fully appreciate, though, is how an ultra-sporting car responds to the driver’s touch when driven as its maker intended. True the Roadster is undoubtedly easier to drive, but I’m not sure that’s such a high priority in such a car: I want cars like this to challenge and involve, and so long as they are not actively dangerous, which neither SLS is remotely, I’d always choose to put a little more in and take a little more out. Which is what the closed SLS allows. To me its steering seemed sharper, its reactions quicker, its body control in extremis that little bit better.
For Mercedes and its customers wealthy enough to consider an SLS, it’s a nice problem to have. Whichever one they choose, the strength of its essential proposition remains: for this kind of money you could have a Ferrari, a McLaren or a Lamborghini, cars with more exotic names, shapes and reputations. Point to point I strongly suspect any one of them would be quicker than either SLS too. But not by much, and the key to the Mercedes’ appeal is precisely that it lacks the esoteric status of these low-volume, high-maintenance manufacturers. It is a car that would feel entirely natural to use every day, put 20,000 miles under its wheels each year and regard not as an occasional treat when the right occasion presents itself, but a way of enhancing your quality of life on the move every time you needed to travel.
Indeed the SLS still feels like a car without a true rival: an Audi R8 is too mainstream, a Bentley Continental Supersports too soft and any of the aforementioned supercars too eclectic. Perhaps that’s why Porsche is feverishly preparing its own answer to the SLS. Until it does, Mercedes appears likely to keep the patch to itself and, open or closed but preferably closed, it will continue to do so on merit.
Engine 6.2 litres, eight cylinders
Top speed 197mph
Power 563bhp at 6800rpm
Fuel/co2 21.4mpg, 308g/km