The front spoiler, the rear apron, sill panels, as well as changes to the body in the area of the rear window (C-pillar) and the trunk lid improved the aerodynamics. For aerodynamic reasons, the rear window was flattened and the tailgate made of light, glass fiber reinforced plastic raised by approximately 40 mm for better air flow. The changes in the rear area resulted in lower lift forces and better straight-line stability. In addition, the windscreen was glued in – and not, as with the other E30 models, framed with a window rubber and piping. As a result, the M3 achieved a relatively low drag coefficient of Cd=0. 33 instead of 0. 38 as in the standard 3 Series. The only exterior body panels the regular 3 Series and the M3 shared were the bonnet, roof panel, sunroof and inner door panels.