The Bugatti Veyron 16.4 is a potent mid-engined hypercar named after Pierre Veyron, a Bugatti development engineer, test driver and company racing driver who, with co-driver Jean-Pierre Wimille, won the 1939 24 Hours of Le Mans while driving a Bugatti. The "EB" refers to Bugatti founder Ettore Bugatti. Named the 2000s Car of the Decade by Top Gear, the standard Veyron also won Top Gear's Best Car Driven All Year award in 2005. Power comes from a 1001 bhp 8.0-litre, quad-turbocharged W16, equivalent to two narrow-angle V8s bolted together, driving all four wheels through the Haldex Traction system and a seven-speed dual-clutch automatic transmission with magnesium shift paddles and a shift time of less than 150 milliseconds. The Veyron can be driven in either semi-automatic or fully-automatic mode. It uses special Michelin PAX run-flat tyres, designed specifically to accommodate the Veyron's 253mph top speed. In order to unlock the car’s full potential, the driver must toggle a special key located next to their seat, which triggers a checklist to establish whether the car and its driver are ready. If so, the rear spoiler retracts, the front air diffusers shut, and the standard 12.5 cm (4.9-inches) ground clearance drops to 6.5 cm (2.6-inches). The Veyron's brakes use cross drilled, radially vented carbon fibre reinforced silicon carbide (C/SiC) composite discs, manufactured by SGL Carbon, which have less brake fade and weigh less than standard cast iron discs. The lightweight aluminium alloy monobloc brake callipers are made by AP Racing; the front callipers have eight titanium pistons and the rears have six pistons. As an added safety feature in the event of brake failure, an anti-lock braking system (ABS) has also been installed on the handbrake. At speeds above 124 mph, the rear wing also acts as an airbrake, snapping to a 55-degree angle in 0.4 seconds once brakes are applied. The targa top version of the Bugatti Veyron EB 16.4, dubbed the Bugatti Veyron 16.4 Grand Sport, was unveiled at the 2008 Pebble Beach Concours d'Elegance. It has extensive reinforcements to compensate for the lack of a standard roof, as well as small changes to the windscreen and running lights. The Grand Sport was limited to 150 units, with the first 50 going exclusively to registered Bugatti customers.