From E30 Zone Wiki
The Cabriolet was a body style available for the E30. When the car was officially launched in 1983, customers could order a roof conversion on any standard 2-door saloon model, performed by Baur. The modification involved removing a large section of the roof panel and the rear window. but retaining the B- and C-pillars and roof gutter, bridged across the vehicle by a stiffening bar. The car then kept its original doors and interior.
Because of the labour, these original Baur cabriolets had very low production numbers (10,865 in Europe, 3,561 in South Africa). Despite their rarity, there are not yet considered desirable or collectable E30 models.
In June 1986 BMW officially launched their own E30 cabriolet, which differed substantially from the Baur version. While the dimensions of the vehicle remained the same, the floorpan was strengthened to allow the B- and C-pillars to be removed above the doorline. Because of these extensive modifications to the shell, the cabriolet shares very little with other E30s in terms of Interior or Bodywork. New buyers are also often confused by the large metal weight in the boot; a 25kg "harmonic damper" placed there by BMW to damp out vibrations caused by lack of body torsional stiffness.
Main article: Cabriolet roof