What is it?
There are lots of big numbers associated with the McLaren 720S Spider, but here's a small one: 12%.
Admittedly, in the context of a car that costs £237,000 and will out-accelerate almost anything the safe side of a competition dragster, any improvement in over-the-shoulder visibility seems an irrelevance. But this is McLaren, and so an incremental gain in this undervalued area of supercar design has been not only made but also quantiifed. As ever, the details really matter.
It’s one of a small number of changes that happen when 720S becomes 720S Spider – a car we've already driven, but until now never on British roads – and results from the use of transparent glazing for the new buttresses, which pivot open when you hold down a toggle on the centre console and peel back the new carbonfibre roof. The whole process takes just 11sec.
Elsewhere, the carbonfibre Monocage II tub has been relieved of its central spine – fairly obviously, as this usually runs lengthways above the cabin – and the rear portion of the structure has been adapted to house the roof and its associated mechanicsm. The new structure is known as the Monocage II-S and remains spectacularly stiff.
The mechanism itself deserves attention, too. Rather than being hydraulic, its uses eight electric motors to silently raise or retract the roof at vehicle speeds of up to 31mph (versus 18mph for the old 650S Spider). It's also light, and with no strengthening required for the tub, the Spider weighs only around 50kg more than the coupé. Its dry weight is a mere 1332kg.
It means that, in terms of performance, there's almost nothing between coupé and Spider. Both hit 62mph in 2.9sec and only by 124mph, which arrives after 7.9sec, does the coupé pull out – and even then, only a nominal tenth. The drawback for Spider owners is that their car is limited to a mere 202mph when the roof is stowed away and head room endless, but even if you live among the German autobahns, this is a technicality, and with the roof in place, you'll manage the full 212mph, just like the coupé.