The BMW Z1 is the first model in BMW's line of Z series roadsters (two-seater convertibles), and was produced in limited numbers from 1989 to 1991. The Z1 is unique for its plastic body panels and vertically sliding doors which drop into the door sills. It is one of the first BMWs to use a multi-link rear suspension. The sole drivetrain specification is the 2.5-litre straight-six engine and 5-speed manual transmission from the E30 325i. In 1996, the Z1's successor, the mass-produced Z3, began production. Development and launch At the start of 1985, BMW set up a division called BMW Technik GmbH to develop concepts for new vehicles and technologies. The director of BMW Technik GmbH was Ulrich Bez, who oversaw the Z1's development. Control of the project was turned over to Klaus Faust when Bez left BMW in October 1988. The lead designer was Harm Lagaay. In August 1985, the BMW board gave approval to further develop the BMW Technik's first concept vehicle, the Z1. A year later, the first road-going prototype was produced and BMW publicly revealed the project. A coupe model was also the subject of a design study, but it did not reach production. In August 1987, BMW announced that the Z1 would enter production and the following month the production form of the Z1 was unveiled at the Frankfurt Motor Show. Production began in October 1988. The original price target was DM 80,000, however by the time production began, the base price had increased to DM 83,000. Doors The doors are unique in that they retract vertically, instead of traditional designs which swing outward or upward (the first car with retractable doors was the 1954 Kaiser Darrin, although those Kaiser Darrin doors slid forwards not downwards). The body with its high sills, offers crash protection independent of the doors, and it is possible (although perhaps not legal in some countries) for the Z1 to be driven with the doors lowered. The windows may be operated independently of the doors, although they do retract automatically if the door is lowered. Both the window and door are driven by electric motors through toothed rubber belts and may be moved manually in an emergency. Body In addition to the unique door design, the Z1 body featured several other innovations: removable plastic body panels, a flat undertray, a roll-hoop integrated into the windscreen surround and continuously zinc welded seams.