The Lotus Type 88 was a technical marvel for its time. It used clever engineering to get around the FIA’s ban on movable aerodynamics. Specifically the movable side skirts that made the famous ground effect cars possible. Ground effects made a massive difference in a cars performance, but created enormous g loads. Which put tremendous stresses on components, components that weren’t really up to the job which created safety concerns, hence the ban. Lotus attempted to get around the new rule by building the Type 88 with 2 chassis. An outer shell and an inner monocoque. At slow speeds with no aero load the outer chassis met the 6mm regulation, however at speed it would get pushed down and create an outer seal which made ground effects possible. While initially approved for its first Grand Prix at Silverstone, public outcry from other teams eventually lead the FIA to ban the car.
Source Motorsport.com & Goodwood Road & Racing