The Lotus 15 is a front-engine sports racing car designed by Colin Chapman of Lotus, built from 1958 until 1960. The 15 is a two-seater, front-engine, rear wheel drive sports racer with an aluminium body over a space frame configuration. As opposed to the six cylinder Bristol 2L engine in its predecessor Lotus Mk.X, the Mk.15 was designed with a dry-sump, all aluminium, DOHC four cylinder Coventry Climax FPF engine of 1.5 to 2.5 Litre displacement built for Formula Two and Grand Prix racing, mated to Lotus' own 5 speed sequential transaxle nicknamed 'Queerbox'. It was designed in 1957, and the production began in late 1957. The spaceframe was similar to Lotus Eleven except for the Chapman strut rear suspension with inboard brakes and the accommodations for a larger engine, which included a slightly (7.5 degrees) tilted engine mounting space on the plan view, shifted to the right of the centerline in the front and left at the rear of the engine. This arrangement gave a larger space for the driver than the normally non-existing passenger. The larger body of "English rolled" aluminum was also similar in appearance to the smaller and successful Lotus 11, with a major difference of a full-width windscreen, and the lower scuttle/screen height. Unlike the 11 which was designed by Frank Costin, the body design was a result of the collaboration between Chapman and the coachbuilder Williams & Pritchard. It was available as a fully assembled form sans the engine at £2885, or as a kit of parts for £2395. By the time the Series 3 was born in 1959, the Lotus transaxle had become more reliable thanks to the Duckworth redesign on its own dry sump lubrication system, but the young engineer pointed out the inherent limitation of the box in the amount of torque it can safely handle. So the Series 3 was offered with the Lotus 'Queer Box' transaxle for 1.5L FPF only, and BMC 4-speed or ZF 5-speed gearbox with a conventional differential for cars with a larger FPF.
