BMW's New Four-Door Coupe

Some 8 years after Mercedes-Benz first launched the CLS-Class, BMW is finally on the verge of revealing its big four-door fastback. Essentially a variant of the 6 Series with two extra doors, the car is expected to debut in mid-2012.

The upcoming four-door car runs on the same 116.8-inch wheelbase as the 5 Series instead of the new 6 Series' 112.4-inch wheelbase. But like the coupe and convertible, the four-door is also wider than a 5 Series at 74.9 inches, and sits on a wider track.

Most important, it is about 3.5 inches lower than a 5 Series, at roughly 54 inches. This low, wide stance is vital to the overall style befitting cars in the so-called four-door coupe category. At 197.1 inches overall, it's 2 inches longer than a Mercedes CLS-Class.

The bodywork retains the frameless door glass of the 6 Series coupe, but there is a B-pillar, so even with all the windows rolled down, it can't provide that open-sided hardtop look.