For the start of the new roadster in 1989, there were two models with three-litre, six-cylinder inline engines (300 SL with 140 kW/190 PS and 300 SL-24 with 170 kW/231 PS as well as four-valve-per-cylinder design) and also the five-litre V8 500 SL model with 240 kW/326 PS (from 1992: 235 kW/320 PS). The development of a top model with a V12 engine was approved by the company in December 1986.
High demands for passive safety go without saying in the development of a new Mercedes-Benz passenger car model series. However, in open vehicles, alongside the conventional accident scenarios, due to the missing solid roof there is also an additional risk in the event of a rollover. Early in the development phase, the fathers of the R 129 model series therefore considered a targa solution in which the B-pillar is expanded to a fixed roll bar. This, however, would have disturbed the classic lines of the roadster.