Despite its Longtail badge, the 600LT Spider has grown by just 7.4cm next to the standard 570S on which it’s based. However, as with the original F1 GTR ‘Longtail’ that lent its name to McLaren’s 21st-century series of go-faster models, the tweaks wrought on the 600LT are more about making the car as capable as possible on track than increasing its overall footprint.

Significantly improved aerodynamics play a central role in achieving this, and Woking’s engineers have introduced a number of changes to the car’s bodywork to make it as limpet-like as possible. These include a wider, more aggressive front splitter that’s been extended by some 27mm; new side sills designed to ‘clean’ turbulent air; a rear diffuser that looks like a grossly oversized set of hair clippers; and a sizeable fixed rear wing. Combined, the improved aerodynamic package of the 600LT Spider develops the same 100kg of downforce at 155mph as it does on the coupé, despite the packaging obstacles the introduction of a convertible roof inevitably bring.

The 10-spoke ultra-lightweight forged alloy wheels and Pirelli P Zero Trofeo R tyres combine to shed 17kg of weight from the 600LT compared with the 570S.

That roof does incur a weight penalty, but it’s a marginal one. The incredible structural rigidity provided by McLaren’s MonoCell II monocoque is key here; without the need for additional bracing, it allowed McLaren’s engineers to implement the same precisionist weight-saving regime introduced on the hard-top. As a result, the 600LT Spider can weigh as much as 100kg less than the convertible 570S on which it’s based – with the right options boxes ticked. On MIRA’s scales, our test car came in at 1465kg.

Elsewhere, the car’s 3.8-litre twin-turbocharged V8 now produces 592bhp – 30bhp more than in the 570S. Some 457lb ft of torque is now developed between 3500-6500rpm, too. The shorter length of the lighter stainless steel top-exit exhausts played a role in extracting this additional potency, while a motorsport-derived flat-plane crankshaft also allows the engine to be positioned lower down in the chassis for a more competitive centre of gravity.

Drive is sent to the rear wheels (which are shod in supersticky Trofeo R rubber) via a seven-speed dual-clutch automatic gearbox. Lastly, the 600LT also makes use of the same lightweight aluminium double-wishbone suspension componentry as its 720S big brother, which is complemented by coil springs and adaptive dampers. The front and rear anti-roll bars have been stiffened for greater response and stability, while the front track has also been widened by 10mm.

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