There is a simple method for deciding how successful a conversion from coupe to convertible has been. The harder it is to spot any differences - be they dynamic or cosmetic - the greater the achievement for carmaker in question.
Sitting here two days after I drove the new MP4-12C Spider, I still can't think of any discernable dynamic difference between it and the coupe. It steers the same, it rides the same, it feels a little bit quicker than the last coupe I drove because it benefits from the 625hp upgrade coming for 2013 and now available as a retrofit to all earlier cars.
According to the rule, that must make it a blinding bit of kit.
A stiff test
One of the main advantages of the McLaren's carbon tub is that removing the roof panel has no detrimental effect on chassis stiffness. The electric folding hardtop and the electric rear glass window add 40kg to the kerb weight, but I really couldn't feel any difference on the road or the track. Perhaps if you ran the two versions back-to-back you might notice a little extra laziness, some extra brake fade and the tyres letting go a touch sooner, but McLaren's main development honcho Chris Goodwin says "it takes quite a bit of time to spot them."
So dynamically, it's very much as you were. By that we mean intriguing, talented, banzai-fast and just very occasionally baffling. On the road the car really shines: it copes with changing surfaces better than any other car of its type and the driver has several different configurations to chose from - most of which are actually usable. The exception is the Track chassis mode which is just too stiff for the road.
This is now version 10 of the McLaren powertrain project, which is something the company is trying to present as a positive example of the way it intends to continuously develop cars throughout their lifetime. It's a nice attempt at parrying criticism of the car not being quite finished at launch, but we're not fooled. In the road car world, one version done well and from the start tends to be preferable.
Upgrade programme
Anyway, I've always thought the powertrain was excellent, if a little lacking in some low-speed calibration. That's now fixed, and they've added more poke and a three-stage Intake Sound Generator which allows the driver three choices of noise level for each of the three powertrain modes. Yes, there's much to fiddle with here. This really is an anytime, anywhere machine. In full auto mode it will pootle with buses, in manual mode it feels as fast as anything I've driven this year. It also now sounds far more aggressive.
The foldable hardtop roof takes a claimed 17 seconds to open or close, and when closed the gap under the tonneau has two snazzy little bags which can hold some extra clobber, meaning the Spider actually has more luggage space than the coupe. You can raise or lower the roof at up to 19mph.
Roof-down you have all the advantages of open-air motoring, if indeed you want them. I have to say the wind-management in the cabin isn't all that impressive: at 85mph it's cascading around and those rear buttresses protrude just enough to have air rip off them and cause quite a bit of unwanted noise. I haven't driven a 458 Spider, but I gather it is slightly better in this respect.
Rugged and windswept
Roof up it's a little noisier than the coupe, but not too bad and you have the extra benefit of being able to drop that electric rear screen and allow more exhaust noise into the cabin.
There are two tyre options: both Pirelli. The standard P-Zero is a fine road tyre, the optional Corsa brings extra track performance, but I thought the basic P-Zero, even though less grippy gave a nicer balance on the track when hot because it allowed the car some more rear slip.
The car costs £195,500, or £19,500 more than the coupe. I'd personally steer clear of the optional carbon ceramic brakes because the pedal feel is still a little bit disconcerting, but otherwise it's not hard to see why McLaren expects 80 per cent of all 12C sales next year to be Spiders.
Me? I don't especially like convertibles, so I'd save the money and have a coupe because you still get that brilliant latest-spec powertrain, but the Spider remains a clever, if obvious expansion of the McLaren brand.
SPECIFICATION | MCLAREN MP4-12C SPIDER
Engine: 3,799cc, twin-turbo V8
Transmission: 7-speed SSG twin-clutch auto, rear-wheel drive
Power (hp): 625@7,500rpm
Torque (lb ft): 442@3,000rpm
0-62mph: 3.1 sec (with optional Pirelli P Zero Corsa tyres)
Top speed: 204mph
Weight: 1,376kg ('dry')
MPG: 24.2mpg (NEDC combined)
CO2: 279g/km
Price: £195,500
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