Imagine that you already make the fastest, most futuristic looking and dynamically excellent supercar this side of half a million euros. What can you do to make it even better? The answer is simple - give it a folding roof.
“The only way to develop a Spider with no loss of dynamics compared to the Coupe is to create both versions in parallel,” explained Andrew Kay, Chief Engineer for the 720S Spider project. “We factored this in from day one, only putting Spider development on hold temporarily while we launched the Coupe in 2017.”
While exposure to the elements via a folding roof delivers a more visceral and rewarding ‘closer to nature’ driving experience, the price normally paid is a significantly diminished structural stiffness that takes its toll on handling and grip.
McLaren neatly sidesteps this by building their cars around a carbon-fibre central tub that does not rely on the roof panel for stiffness. Equally stiff whether open or closed, this immensely strong but light tub supports the front and rear sub-frames, and also forms the passenger crash protection cell.
Adaptation of the 720S Coupe’s Monocage II carbon-fibre tub to open duties was comprehensive enough for it to be named Monocage II-S. Major bespoke features of this new tub are the carbon-fibre rollover protection system (ROPS) that saves 6.8kg over the steel components used in the 650S Spider, and the storage compartment for the folding roof.
Being at the highest point of the car’s structure, the lighter components help to lower the centre of gravity and the dynamic roll couple. As part of the primary and secondary safety brief, they were also designed to enhance over-the shoulder visibility and provide the anchor points for the seatbelts and folding roof system.
With the loss of the Ford GT40 style doors that ease ingress and egress to the Coupe by taking big bites out of the roof panel, McLaren had to re-jig the hinge mechanism of the dihedral doors to suit the Spider.
The new one-piece folding roof is much neater than the older style two-piece system used on the 570S and 600LT Spiders. It is also much faster in operation, taking a scant 11 seconds to go from closed to open and vice versa. Apart from saving six whole seconds, the new roof can be operated at speeds up to 50km/h as opposed to the 40km/h of the older two-piece system.
A worthwhile cost option is the electronically actuated crystal glass roof panel that effectively blocks 95% of sunlight and ultra-violet light to keep the interior cool while the car is parked or running under the hot sun. This panel goes transparent at the touch of a button, flooding the cabin with light on a dull day.
Meanwhile, the smart air-conditioning system adjusts to open and closed cabin environments, while the electrically adjustable rear windscreen can be raised or lowered to act as a tuneable wind deflector.
Rearward visibility is always an issue in a mid-engine supercar, and the greenhouse of the 720S Coupe was outstanding in the way it opened up a superior over-the-shoulder view than any of its competitors.
The Spider version maximises both rear and over-shoulder visibility by using glazed rear three quarter panels and glass sections in the flying buttresses that normally create tunnel vision to the rear. The practical effectiveness of these features is immediately apparent when you glance in the rear view mirror and are surprised by the impressive view aft.
While there is no escaping the extra weight added by the folding roof mechanism and reinforced structure that makes the Spider 49kg heavier than its Coupe sister, it still shows a 38kg saving over the 650S Spider.
That said, raising the class bar is always the ultimate arbiter of progress, and the greater use of structural carbon-fibre makes the 1,232kg (dry weight) 720S Spider the lightest car in its class. It shades the second-lightest-in-class Ferrari 488 Spider by a whopping 88kg, while besting it hands down for structural stiffness.
Paper numbers are one thing, but against the stopwatch the extra 38kg borne by the 720S Spider - equivalent to about half a passenger - hardly impacts its prodigious performance.
When all the numbers are crunched the flagship McLaren Spider is one of a handful of current production cars that can exceed 200mph with its roof down. The exact number is 325km/h, or a more impressive sounding 202mph, which sounds pretty insane for al fresco driving. The 212mph (341km/h) Vmax with the roof up matches the Coupe exactly, and will unquestionably feel a lot less dramatic.
The 720S Spider’s intergalactic pace is provided by the identical M840T McLaren’s twin turbo flat plane crank V8 as powers the Coupe. Making 720hp at 7,250rpm, and 770Nm of torque at 5,500rpm, it blasts both 720S variants to 100km/h in the same 2.9 sec, with 200km/h and 300km/h coming up in just 7.9 sec (Coupe 7.8 sec) and 22.4 sec (Coupe 21.4 sec) respectively, and the quarter-mile post pipped at just 10.4 sec (Coupe 10.3 sec).
Today we are in Arizona for our test drive, and we were warned not to risk upsetting local law enforcement by attempting anything near those kinds of speeds. But there is nothing to say we can’t scoot from rest to a legal 100km/h in the 2.9 sec that McLaren claims.
Thanks to the weight of its engine over the rear wheels and 4WD traction, the much less powerful Porsche 911 Turbo S is usually one of the fastest supercars off the line, but McLaren’s clever launch control puts the rear-wheel-drive 720S in a similar league on the 0-100km/h sprint.
Thereafter the 720S consigns the Porsche and other major league competitors like the Lamborghini Aventador to the rear view mirror, its lower weight, superior power-to-weight ratio, and cutting edge aerodynamics placing it firmly at the head of the pack.
The 4.0 litre flat-plane crank bi-turbo V8 has come a long way since the original core of this motor debuted in 3.8 litre form in the MP4-12C of 2011. Power, torque, smoothness, pickup, efficiency and soundtrack have all been steadily improved in the intervening years, and the latest incarnation is the best yet.
The other McLaren technology that has come on in leaps and bounds is their active suspension, which is a quite different animal from any other system on the planet.
The latest version of this in-house developed system that underpins the 720S family feels much more transparent to the driver than the MP4-12C iteration, which sometimes left you guessing what the suspension was going to do next.
On Arizona highways as well as urban and country roads, this active suspension impressed with its supple secondary ride in Comfort mode, while its iron fisted body control in Sport mode made short work of challenging twisty roads. Its ability to avert body roll in bends and level the wheels over undulations seems supernatural at times, almost to the point of making you feel invincible.
The 720S is capable of astounding pace across country with little noticeable effort, which makes it a civilised supercar able to tuck long distances under its belt without stressing out its occupants. Perhaps ironically then the Spider’s abilities as a long distance cruiser turn out to be superior to the Coupe’s in terms of cabin refinement.
On the press launch in Rome in mid-2017 I noticed that the tyre rotational noise of the 720S Coupe was significantly greater than in the 570GT. This memory stuck with me and I was somewhat surprised that tyre noise in the 720S Spider fell somewhere in between.
When I mentioned this to Andrew Kay, he thought about it for a moment and then explained that the smaller cabin volume behind the seats in the Spider, and the tray into which the roof folds has changed the resonance characteristics of the structure in a way that significantly reduces the road noise reaching the cabin.
While the McLaren 720S Coupe delivers a big win, the 720S Spider delivers a win, win. It is simply the fastest, most futuristic looking, dynamically excellent, and complete supercar this side of half a million euros.